Something that does NOT show up in virus and antispyware scans altered something on my PC, so that explorer.exe opens repeatedly with "search' activated. Close the file, 2 more pop up. Try to delete/rename explorer.exe, and a new one appears.

Below my ht log:

Logfile of HijackThis v1.99.1
Scan saved at 3:33:08 AM, on 11/6/2006
Platform: Windows XP SP1 (WinNT 5.01.2600)
MSIE: Internet Explorer v6.00 SP2 (6.00.2900.2180)

Running processes:
C:\WINNT\System32\smss.exe
C:\WINNT\system32\csrss.exe
C:\WINNT\system32\winlogon.exe
C:\WINNT\system32\services.exe
C:\WINNT\system32\lsass.exe
C:\WINNT\system32\svchost.exe
C:\WINNT\System32\svchost.exe
C:\WINNT\System32\svchost.exe
C:\WINNT\system32\spoolsv.exe
C:\WINNT\System32\svchost.exe
C:\Program Files\Network ICE\blackd.exe
E:\nortonsw\Norton Antivirus\navapsvc.exe
E:\nod32\nod32krn.exe
E:\nortonsw\Norton Antivirus\SAVScan.exe
C:\Program Files\Common Files\Symantec Shared\CCPD-LC\symlcsvc.exe
C:\WINNT\System32\wdfmgr.exe
C:\WINNT\Explorer.EXE
C:\Program Files\Synaptics\SynTP\SynTPLpr.exe
C:\Program Files\Synaptics\SynTP\SynTPEnh.exe
C:\WINNT\System32\wuauclt.exe
C:\WINNT\System32\svchost.exe
G:\firefox\firefox.exe
G:\avg\guard.exe
G:\avg\avgas.exe
C:\Program Files\Common Files\Symantec Shared\NMain.exe
G:\avg\other av programs\HijackThis.exe

R0 - HKCU\Software\Microsoft\Internet Explorer\Main,Start Page = http://www.free-software-forever.com/
R1 - HKLM\Software\Microsoft\Internet Explorer\Main,Default_Page_URL = http://www.gatewaybiz.com
R0 - HKLM\Software\Microsoft\Internet Explorer\Main,Start Page = http://www.free-software-forever.com
R1 - HKCU\Software\Microsoft\Internet Connection Wizard,ShellNext = http://www.gatewaybiz.com/
R3 - URLSearchHook: Yahoo! Toolbar - {EF99BD32-C1FB-11D2-892F-0090271D4F88} - C:\Program Files\Yahoo!\Companion\Installs\cpn\yt.dll
O2 - BHO: DAPHelper Class - {0000CC75-ACF3-4cac-A0A9-DD3868E06852} - D:\DAP50\dapbho.dll
O2 - BHO: Yahoo! Toolbar Helper - {02478D38-C3F9-4EFB-9B51-7695ECA05670} - C:\Program Files\Yahoo!\Companion\Installs\cpn\yt.dll
O2 - BHO: AcroIEHlprObj Class - {06849E9F-C8D7-4D59-B87D-784B7D6BE0B3} - C:\Program Files\Adobe\Acrobat 7.0\ActiveX\AcroIEHelper.dll
O2 - BHO: Yahoo! IE Services Button - {5BAB4B5B-68BC-4B02-94D6-2FC0DE4A7897} - C:\Program Files\Yahoo!\Common\yiesrvc.dll
O2 - BHO: PCTools Site Guard - {5C8B2A36-3DB1-42A4-A3CB-D426709BBFEB} - E:\SPYWAR~1\tools\iesdsg.dll
O2 - BHO: (no name) - {6aa1f394-ffc5-4c27-9fc4-215ae605a174} - (no file)
O2 - BHO: SSVHelper Class - {761497BB-D6F0-462C-B6EB-D4DAF1D92D43} - C:\Program Files\Java\jre1.5.0_06\bin\ssv.dll
O2 - BHO: PCTools Browser Monitor - {B56A7D7D-6927-48C8-A975-17DF180C71AC} - E:\SPYWAR~1\tools\iesdpb.dll
O2 - BHO: CNavExtBho Class - {BDF3E430-B101-42AD-A544-FADC6B084872} - E:\nortonsw\Norton Antivirus\NavShExt.dll
O3 - Toolbar: DAP Bar - {62999427-33FC-4baf-9C9C-BCE6BD127F08} - D:\DAP50\DAPIEBar.dll
O3 - Toolbar: Norton AntiVirus - {42CDD1BF-3FFB-4238-8AD1-7859DF00B1D6} - E:\nortonsw\Norton Antivirus\NavShExt.dll
O3 - Toolbar: Yahoo! Toolbar - {EF99BD32-C1FB-11D2-892F-0090271D4F88} - C:\Program Files\Yahoo!\Companion\Installs\cpn\yt.dll
O4 - HKLM\..\Run: [SynTPLpr] C:\Program Files\Synaptics\SynTP\SynTPLpr.exe
O4 - HKLM\..\Run: [SynTPEnh] C:\Program Files\Synaptics\SynTP\SynTPEnh.exe
O4 - HKLM\..\Run: [ATIPTA] C:\Program Files\ATI Technologies\ATI Control Panel\atiptaxx.exe
O4 - HKLM\..\Run: [StacSysTray] C:\Program Files\SigmaTel\C-Major Audio\ControlPanel\StacSysTray.exe
O4 - HKLM\..\Run: [ccApp] "c:\Program Files\Common Files\Symantec Shared\ccApp.exe"
O4 - HKLM\..\Run: [AGRSMMSG] AGRSMMSG.exe
O4 - HKLM\..\Run: [!AVG Anti-Spyware] "G:\avg\avgas.exe" /minimized
O6 - HKCU\Software\Policies\Microsoft\Internet Explorer\Control Panel present
O8 - Extra context menu item: &Download with &DAP - D:\DAP50\dapextie.htm
O8 - Extra context menu item: &Yahoo! Search - file:///C:\Program Files\Yahoo!\Common/ycsrch.htm
O8 - Extra context menu item: Download &all with DAP - D:\DAP50\dapextie2.htm
O8 - Extra context menu item: E&xport to Microsoft Excel - res://C:\PROGRA~1\MI1933~1\Office10\EXCEL.EXE/3000
O8 - Extra context menu item: Yahoo! &Dictionary - file:///C:\Program Files\Yahoo!\Common/ycdict.htm
O8 - Extra context menu item: Yahoo! &Maps - file:///C:\Program Files\Yahoo!\Common/ycmap.htm
O8 - Extra context menu item: Yahoo! &SMS - file:///C:\Program Files\Yahoo!\Common/ycsms.htm
O9 - Extra button: (no name) - {08B0E5C0-4FCB-11CF-AAA5-00401C608501} - C:\Program Files\Java\jre1.5.0_06\bin\npjpi150_06.dll
O9 - Extra 'Tools' menuitem: Sun Java Console - {08B0E5C0-4FCB-11CF-AAA5-00401C608501} - C:\Program Files\Java\jre1.5.0_06\bin\npjpi150_06.dll
O9 - Extra button: Spyware Doctor - {2D663D1A-8670-49D9-A1A5-4C56B4E14E84} - E:\SPYWAR~1\tools\iesdpb.dll
O9 - Extra button: Yahoo! Services - {5BAB4B5B-68BC-4B02-94D6-2FC0DE4A7897} - C:\Program Files\Yahoo!\Common\yiesrvc.dll
O9 - Extra button: Real.com - {CD67F990-D8E9-11d2-98FE-00C0F0318AFE} - C:\WINNT\System32\Shdocvw.dll
O9 - Extra button: Yahoo! Messenger - {E5D12C4E-7B4F-11D3-B5C9-0050045C3C96} - C:\Program Files\Yahoo!\Messenger\YahooMessenger.exe
O9 - Extra 'Tools' menuitem: Yahoo! Messenger - {E5D12C4E-7B4F-11D3-B5C9-0050045C3C96} - C:\Program Files\Yahoo!\Messenger\YahooMessenger.exe
O9 - Extra button: Messenger - {FB5F1910-F110-11d2-BB9E-00C04F795683} - C:\Program Files\Messenger\msmsgs.exe
O9 - Extra 'Tools' menuitem: Windows Messenger - {FB5F1910-F110-11d2-BB9E-00C04F795683} - C:\Program Files\Messenger\msmsgs.exe
O9 - Extra button: Microsoft AntiSpyware helper - {D96DE37B-C27E-40B8-9D7D-DF919E8C9271} - (no file) (HKCU)
O9 - Extra 'Tools' menuitem: Microsoft AntiSpyware helper - {D96DE37B-C27E-40B8-9D7D-DF919E8C9271} - (no file) (HKCU)
O14 - IERESET.INF: START_PAGE_URL=http://www.free-software-forever.com/
O14 - IERESET.INF: MS_START_PAGE_URL=http://www.free-software-forever.com/
O16 - DPF: {0E5F0222-96B9-11D3-8997-00104BD12D94} (PCPitstop Utility) - http://support.gateway.com/support/profiler/PCPitStop.CAB
O16 - DPF: {17492023-C23A-453E-A040-C7C580BBF700} (Windows Genuine Advantage Validation Tool) - http://go.microsoft.com/fwlink/?linkid=36467&clcid=0x409
O16 - DPF: {1D0D9077-3798-49BB-9058-393499174D5D} - file://c:\counter.cab
O16 - DPF: {1F2F4C9E-6F09-47BC-970D-3C54734667FE} (LSSupCtl Class) - http://www.symantec.com/techsupp/asa/ctrl/LSSupCtl.cab
O16 - DPF: {30528230-99f7-4bb4-88d8-fa1d4f56a2ab} (YInstStarter Class) - C:\Program Files\Yahoo!\Common\yinsthelper.dll
O16 - DPF: {4F1E5B1A-2A80-42CA-8532-2D05CB959537} (MSN Photo Upload Tool) - http://by20fd.bay20.hotmail.msn.com/resources/MsnPUpld.cab
O16 - DPF: {97BB6657-DC7F-4489-9067-51FAB9D8857E} (CWebLaunchCtl Object) - http://support.gateway.com/eSupport/static.../weblaunch2.cab
O16 - DPF: {9A57B18E-2F5D-11D5-8997-00104BD12D94} (compid Class) - https://support.gateway.com/support/serialharvest/gwCID.CAB
O16 - DPF: {CE28D5D2-60CF-4C7D-9FE8-0F47A3308078} (ActiveDataInfo Class) - http://www.symantec.com/techsupp/asa/ctrl/SymAData.cab
O18 - Filter: text/html - (no CLSID) - (no file)
O20 - Winlogon Notify: mqqrvc - mqqrvc.dll (file missing)
O23 - Service: Automatic LiveUpdate Scheduler - Symantec Corporation - C:\Program Files\Symantec\LiveUpdate\ALUSchedulerSvc.exe
O23 - Service: AVG Anti-Spyware Guard - Anti-Malware Development a.s. - G:\avg\guard.exe
O23 - Service: BlackICE - Internet Security Systems, Inc. - C:\Program Files\Network ICE\blackd.exe
O23 - Service: Symantec Event Manager (ccEvtMgr) - Symantec Corporation - C:\Program Files\Common Files\Symantec Shared\ccEvtMgr.exe
O23 - Service: Symantec Password Validation (ccPwdSvc) - Symantec Corporation - C:\Program Files\Common Files\Symantec Shared\ccPwdSvc.exe
O23 - Service: Symantec Settings Manager (ccSetMgr) - Symantec Corporation - C:\Program Files\Common Files\Symantec Shared\ccSetMgr.exe
O23 - Service: InstallDriver Table Manager (IDriverT) - Macrovision Corporation - C:\Program Files\Common Files\InstallShield\Driver\1050\Intel 32\IDriverT.exe
O23 - Service: LiveUpdate - Symantec Corporation - C:\PROGRA~1\Symantec\LIVEUP~1\LUCOMS~2.EXE
O23 - Service: Norton AntiVirus Auto Protect Service (navapsvc) - Symantec Corporation - E:\nortonsw\Norton Antivirus\navapsvc.exe
O23 - Service: NOD32 Kernel Service (NOD32krn) - Eset - E:\nod32\nod32krn.exe
O23 - Service: MaxSyncService (NTService1) - - C:\Program Files\Maxtor\OneTouch\Utils\SyncServices.exe
O23 - Service: Sigmatel PassThru (PassThru) - Unknown owner - C:\Program Files\SigmaTel\C-Major Audio\ControlPanel\passthru.exe
O23 - Service: SAVScan - Symantec Corporation - E:\nortonsw\Norton Antivirus\SAVScan.exe
O23 - Service: ScriptBlocking Service (SBService) - Symantec Corporation - C:\PROGRA~1\COMMON~1\SYMANT~1\SCRIPT~1\SBServ.exe
O23 - Service: PC Tools Spyware Doctor (SDhelper) - PC Tools Research Pty Ltd - E:\Spyware Doctor\sdhelp.exe
O23 - Service: Symantec Network Drivers Service (SNDSrvc) - Symantec Corporation - C:\Program Files\Common Files\Symantec Shared\SNDSrvc.exe
O23 - Service: Symantec Core LC - Symantec Corporation - C:\Program Files\Common Files\Symantec Shared\CCPD-LC\symlcsvc.exe
O23 - Service: SymWMI Service (SymWSC) - Symantec Corporation - C:\Program Files\Common Files\Symantec Shared\Security Center\SymWSC.exe

Please download SilentRunners from here:
http://www.silentrunners.org/Silent%20Runners.zip

Unzip it to the desktop and double-click on it.
Silent Runners will ask if you want to skip the supplementary search.
Please select 'No' to include them.
The program will take longer to run, but will give us more information.

If you get any kind of warning message about scripts, please choose to allow the script to run.

When the scan is finished, a message will pop up and a logfile will have been created on the desktop.
The logfile is named 'Startup Programs' by default and will be located where the program is.

Please post the entire contents of this logfile for me to see.

Late reply, but I had to reinstall the OS. After a while of endless popup's, got errors that memory could not be written etc.
All this "trojan" hunting took too long, so I just re-installed the OS and all is fine now.