Nothing detected anywhere--but still hijacked

I use Firefox for most browsing, but IE is still a necessity from time to time. However, when using IE, I have two behaviors occurring:

1 - I get a pop-up ad that advertises various sites. If the window is left open, it refreshes itself to become a new ad.

2 - Various words on certain webpages are underlined and hyperlinked. I do not want to click the links for fear of what may happen.

My problem is that I only have on BHO, belonging to a SPyware removal tool. I have used half a dozen different tools, from hijackthis, AdAware, Spybot S&D, and plenty more. I have run a registry cleaner, scanned for viruses using three separate scanners, and come up short. Does anyone have a clue?

Logfile of HijackThis v1.98.2
Scan saved at 7:59:03 PM, on 7/9/2005
Platform: Windows XP SP2 (WinNT 5.01.2600)
MSIE: Internet Explorer v6.00 SP2 (6.00.2900.2180)

Running processes:
C:\WINDOWS\System32\smss.exe
C:\WINDOWS\system32\winlogon.exe
C:\WINDOWS\system32\services.exe
C:\WINDOWS\system32\lsass.exe
C:\WINDOWS\system32\Ati2evxx.exe
C:\WINDOWS\system32\svchost.exe
C:\WINDOWS\System32\svchost.exe
C:\WINDOWS\system32\spoolsv.exe
C:\WINDOWS\system32\Ati2evxx.exe
C:\WINDOWS\Explorer.EXE
C:\WINDOWS\system32\CTHELPER.EXE
C:\WINDOWS\system32\ati3d1ag.exe
C:\Program Files\Alwil Software\Avast4\aswUpdSv.exe
C:\WINDOWS\System32\CTsvcCDA.exe
C:\Program Files\FSI\F-Prot\fpavupdm.exe
C:\WINDOWS\System32\svchost.exe
C:\WINDOWS\system32\UAService7.exe
C:\WINDOWS\System32\MsPMSPSv.exe
C:\Program Files\Mozilla Firefox\firefox.exe
C:\Program Files\Windows Media Player\wmplayer.exe
C:\Program Files\hijackthis\HijackThis.exe

R0 - HKCU\Software\Microsoft\Internet Explorer\Main,Start Page = http://www.yahoo.com/
R0 - HKCU\Software\Microsoft\Internet Explorer\Main,Local Page =
R0 - HKLM\Software\Microsoft\Internet Explorer\Main,Local Page =
O2 - BHO: (no name) - {5C8B2A36-3DB1-42A4-A3CB-D426709BBFEB} - (no file)
O4 - HKLM\..\Run: [CTHelper] CTHELPER.EXE
O4 - HKLM\..\Run: [db31193371aa] C:\WINDOWS\system32\ati3d1ag.exe
O4 - HKLM\..\Run: [F-StopW] C:\Program Files\FSI\F-Prot\F-StopW.EXE
O9 - Extra button: Spyware Doctor - {2D663D1A-8670-49D9-A1A5-4C56B4E14E84} - (no file)
O9 - Extra button: AIM - {AC9E2541-2814-11d5-BC6D-00B0D0A1DE45} - C:\Program Files\AIM\aim.exe
O10 - Broken Internet access because of LSP provider 'xfire_lsp_11078.dll' missing
O16 - DPF: {F54C1137-5E34-4B95-95A5-BA56D4D8D743} (Secure Delivery) - http://www.gamespot.com/KDX/kdx.cab

Thanks for your help. Here is the updated file with the latest version:

Logfile of HijackThis v1.99.1
Scan saved at 9:56:05 AM, on 7/10/2005
Platform: Windows XP SP2 (WinNT 5.01.2600)
MSIE: Internet Explorer v6.00 SP2 (6.00.2900.2180)

Running processes:
C:\WINDOWS\System32\smss.exe
C:\WINDOWS\system32\winlogon.exe
C:\WINDOWS\system32\services.exe
C:\WINDOWS\system32\lsass.exe
C:\WINDOWS\system32\Ati2evxx.exe
C:\WINDOWS\system32\svchost.exe
C:\WINDOWS\System32\svchost.exe
C:\WINDOWS\system32\spoolsv.exe
C:\WINDOWS\system32\Ati2evxx.exe
C:\WINDOWS\Explorer.EXE
C:\WINDOWS\system32\CTHELPER.EXE
C:\Program Files\Alwil Software\Avast4\aswUpdSv.exe
C:\WINDOWS\system32\ati2sgag.exe
C:\Program Files\Alwil Software\Avast4\ashServ.exe
C:\Documents and Settings\Owner\Desktop\System Tools\HijackThis.exe

R0 - HKCU\Software\Microsoft\Internet Explorer\Main,Start Page = http://www.yahoo.com/
O4 - HKLM\..\Run: [CTHelper] CTHELPER.EXE
O4 - HKLM\..\Run: [F-StopW] C:\Program Files\FSI\F-Prot\F-StopW.EXE
O9 - Extra button: Spyware Doctor - {2D663D1A-8670-49D9-A1A5-4C56B4E14E84} - C:\WINDOWS\System32\shdocvw.dll
O9 - Extra button: AIM - {AC9E2541-2814-11d5-BC6D-00B0D0A1DE45} - C:\Program Files\AIM\aim.exe
O10 - Broken Internet access because of LSP provider 'xfire_lsp_11078.dll' missing
O20 - Winlogon Notify: Zboard - C:\WINDOWS\SYSTEM32\Winlognotif.dll
O23 - Service: Adobe LM Service - Unknown owner - C:\Program Files\Common Files\Adobe Systems Shared\Service\Adobelmsvc.exe
O23 - Service: avast! iAVS4 Control Service (aswUpdSv) - Unknown owner - C:\Program Files\Alwil Software\Avast4\aswUpdSv.exe
O23 - Service: Ati HotKey Poller - ATI Technologies Inc. - C:\WINDOWS\system32\Ati2evxx.exe
O23 - Service: ATI Smart - Unknown owner - C:\WINDOWS\system32\ati2sgag.exe
O23 - Service: avast! Antivirus - Unknown owner - C:\Program Files\Alwil Software\Avast4\ashServ.exe
O23 - Service: avast! Mail Scanner - Unknown owner - C:\Program Files\Alwil Software\Avast4\ashMaiSv.exe" /service (file missing)
O23 - Service: avast! Web Scanner - Unknown owner - C:\Program Files\Alwil Software\Avast4\ashWebSv.exe" /service (file missing)
O23 - Service: Creative Service for CDROM Access - Creative Technology Ltd - C:\WINDOWS\System32\CTsvcCDA.exe
O23 - Service: F-Prot Antivirus Update Monitor - FRISK Software - C:\Program Files\FSI\F-Prot\fpavupdm.exe
O23 - Service: InstallDriver Table Manager (IDriverT) - Macrovision Corporation - C:\Program Files\Common Files\InstallShield\Driver\1050\Intel 32\IDriverT.exe
O23 - Service: iPod Service (iPodService) - Unknown owner - C:\Program Files\iPod\bin\iPodService.exe (file missing)
O23 - Service: SecuROM User Access Service (V7) (UserAccess7) - Unknown owner - C:\WINDOWS\system32\UAService7.exe

So far, everything in IE looks to be performing normally.