Help !! des virus m'envahissent....

Bonjour,
avast me trouve plein de virus et n'arrive pas à les éliminer, tel que SdBot, Trojan-gen, Nulprot-B et Tiny-II.....
Que faire ???
voici mon log

Logfile of HijackThis v1.99.1
Scan saved at 17:46:42, on 18/11/2007
Platform: Windows XP SP1 (WinNT 5.01.2600)
MSIE: Internet Explorer v6.00 SP1 (6.00.2800.1106)

Running processes:
C:\WINDOWS\System32\smss.exe
C:\WINDOWS\system32\csrss.exe
C:\WINDOWS\system32\winlogon.exe
C:\WINDOWS\system32\services.exe
C:\WINDOWS\system32\lsass.exe
C:\WINDOWS\system32\svchost.exe
C:\WINDOWS\System32\svchost.exe
C:\WINDOWS\System32\svchost.exe
C:\WINDOWS\System32\svchost.exe
C:\Program Files\Alwil Software\Avast4\aswUpdSv.exe
C:\Program Files\Alwil Software\Avast4\ashServ.exe
C:\WINDOWS\system32\spoolsv.exe
C:\WINDOWS\Explorer.EXE
C:\PROGRA~1\ALWILS~1\Avast4\ashDisp.exe
C:\WINDOWS\SOUNDMAN.EXE
C:\WINDOWS\System32\ctfmon.exe
C:\Program Files\Skype\Phone\Skype.exe
C:\WINDOWS\System32\mdm.exe
C:\WINDOWS\rundll32.exe
C:\Program Files\a-squared Free\a2service.exe
C:\WINDOWS\system\msnrav.exe
C:\Program Files\Internet Explorer\iexplore.exe
C:\Program Files\Hijackthis Version Française\VERSION TRADUITE ORIGINALE.EXE

R1 - HKCU\Software\Microsoft\Internet Explorer\Main,Default_Page_URL = http://www.neuf.fr
R0 - HKCU\Software\Microsoft\Internet Explorer\Main,Start Page = http://dbsarticles.com
R0 - HKCU\Software\Microsoft\Internet Explorer\Toolbar,LinksFolderName = Liens
F2 - REG:system.ini: UserInit=C:\WINDOWS\system32\userinit.exe,C:\WINDOWS\System32\ntos.exe,
O2 - BHO: Aide pour le lien d'Adobe PDF Reader - {06849E9F-C8D7-4D59-B87D-784B7D6BE0B3} - C:\Program Files\Fichiers communs\Adobe\Acrobat\ActiveX\AcroIEHelper.dll
O2 - BHO: Skype add-on (mastermind) - {22BF413B-C6D2-4d91-82A9-A0F997BA588C} - C:\Program Files\Skype\Toolbars\Internet Explorer\SkypeIEPlugin.dll
O2 - BHO: (no name) - {5787A3AA-6775-45BD-9ADC-9E780244109C} - C:\WINDOWS\System32\ddaby.dll
O2 - BHO: (no name) - {BCC73622-F72D-4277-803C-D65565A0947F} - C:\WINDOWS\System32\fccawwt.dll
O3 - Toolbar: &Radio - {8E718888-423F-11D2-876E-00A0C9082467} - C:\WINDOWS\System32\msdxm.ocx
O4 - HKLM\..\Run: [NvCplDaemon] RUNDLL32.EXE C:\WINDOWS\System32\NvCpl.dll,NvStartup
O4 - HKLM\..\Run: [nwiz] nwiz.exe /install
O4 - HKLM\..\Run: [NvMediaCenter] RUNDLL32.EXE C:\WINDOWS\System32\NvMcTray.dll,NvTaskbarInit
O4 - HKLM\..\Run: [Adobe Reader Speed Launcher] "C:\Program Files\Adobe\Reader 8.0\Reader\Reader_sl.exe"
O4 - HKLM\..\Run: [avast!] C:\PROGRA~1\ALWILS~1\Avast4\ashDisp.exe
O4 - HKLM\..\Run: [SoundMan] SOUNDMAN.EXE
O4 - HKLM\..\Run: [KernelFaultCheck] %systemroot%\system32\dumprep 0 -k
O4 - HKLM\..\Run: [Microsoft Office] C:\WINDOWS\System32\mdm.exe
O4 - HKCU\..\Run: [CTFMON.EXE] C:\WINDOWS\System32\ctfmon.exe
O4 - HKCU\..\Run: [MsnMsgr] "C:\Program Files\MSN Messenger\MsnMsgr.Exe" /background
O4 - HKCU\..\Run: [Skype] "C:\Program Files\Skype\Phone\Skype.exe" /nosplash /minimized
O4 - HKCU\..\Run: [BgMonitor_{79662E04-7C6C-4d9f-84C7-88D8A56B10AA}] "C:\Program Files\Fichiers communs\Ahead\Lib\NMBgMonitor.exe"
O4 - HKCU\..\Run: [Microsoft Office] C:\WINDOWS\System32\mdm.exe
O4 - HKCU\..\Run: [Microsoft Windows Driver] C:\WINDOWS\rundll32.exe
O9 - Extra button: Skype - {77BF5300-1474-4EC7-9980-D32B190E9B07} - C:\Program Files\Skype\Toolbars\Internet Explorer\SkypeIEPlugin.dll
O9 - Extra button: Related - {c95fe080-8f5d-11d2-a20b-00aa003c157a} - C:\WINDOWS\web\related.htm
O9 - Extra 'Tools' menuitem: Show &Related Links - {c95fe080-8f5d-11d2-a20b-00aa003c157a} - C:\WINDOWS\web\related.htm
O9 - Extra button: Messenger - {FB5F1910-F110-11d2-BB9E-00C04F795683} - C:\Program Files\Messenger\MSMSGS.EXE
O9 - Extra 'Tools' menuitem: Messenger - {FB5F1910-F110-11d2-BB9E-00C04F795683} - C:\Program Files\Messenger\MSMSGS.EXE
O16 - DPF: {6414512B-B978-451D-A0D8-FCFDF33E833C} (WUWebControl Class) - http://update.microsoft.com/...
O16 - DPF: {C36112BF-2FA3-4694-8603-3B510EA3B465} (Lycos File Upload Component) - http://f010.mail.caramail.lycos.fr/app/uploader/FileUploader.cab
O17 - HKLM\System\CCS\Services\Tcpip\..\{681B434A-386F-4D3E-B99C-B48FC0E89602}: NameServer = 86.64.145.141 84.103.237.141
O18 - Protocol: livecall - {828030A1-22C1-4009-854F-8E305202313F} - C:\PROGRA~1\MSNMES~1\MSGRAP~1.DLL
O18 - Protocol: msnim - {828030A1-22C1-4009-854F-8E305202313F} - C:\PROGRA~1\MSNMES~1\MSGRAP~1.DLL
O18 - Protocol: skype4com - {FFC8B962-9B40-4DFF-9458-1830C7DD7F5D} - C:\PROGRA~1\FICHIE~1\Skype\SKYPE4~1.DLL
O20 - Winlogon Notify: fccawwt - C:\WINDOWS\SYSTEM32\fccawwt.dll
O23 - Service: a-squared Free Service (a2free) - Emsi Software GmbH - C:\Program Files\a-squared Free\a2service.exe
O23 - Service: avast! iAVS4 Control Service (aswUpdSv) - ALWIL Software - C:\Program Files\Alwil Software\Avast4\aswUpdSv.exe
O23 - Service: avast! Antivirus - ALWIL Software - 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: MSN RAV - Unknown owner - C:\WINDOWS\system\msnrav.exe
O23 - Service: NMIndexingService - Unknown owner - C:\Program Files\Fichiers communs\Ahead\Lib\NMIndexingService.exe (file missing)
O23 - Service: NVIDIA Display Driver Service (NVSvc) - NVIDIA Corporation - C:\WINDOWS\System32\nvsvc32.exe