Problème, mon PC freeze

Bonjour,

Depuis quelques jours j'ai des problèmes avec mon pc, il freeze de manière completement irrégulière. Parfois il marche pendant plusieurs heures d'affilée, à d'autres moments il freeze toutes les 5 minutes.
J'ai installé antivir et fait un scan des disques, installé ccleaner, viré tous les fichiers temporaires et réparé les erreurs du registre.

La je viens de faire un rapport avec HijackThis :

Logfile of Trend Micro HijackThis v2.0.2
Scan saved at 18:54:54, on 12/12/2008
Platform: Windows Vista SP1 (WinNT 6.00.1905)
MSIE: Internet Explorer v7.00 (7.00.6001.18000)
Boot mode: Normal

Running processes:
C:\Windows\system32\taskeng.exe
C:\Windows\system32\Dwm.exe
C:\Windows\Explorer.EXE
C:\Program Files\Windows Media Player\wmpnscfg.exe
C:\Windows\System32\mobsync.exe
C:\Program Files\Windows Live\Messenger\msnmsgr.exe
C:\Program Files\Avira\AntiVir PersonalEdition Classic\avgnt.exe
C:\Program Files\Trend Micro\HijackThis\HijackThis.exe

R1 - HKCU\Software\Microsoft\Internet Explorer\Main,Search Page = https://www.bing.com/?toHttps=1&redig=5FC791212101479BAFBE1A679848B1AF
R0 - HKCU\Software\Microsoft\Internet Explorer\Main,Start Page = http://www1.mini20.com/?tm=1&kw=Secure+Web+Search+Engine&KW1=Secure%20Web%20Search%20Engine&KW2=Best%20Malware%20Detection%20And%20Removal%20Software&searchbox=0&domainname=0&backfill=0
R1 - HKLM\Software\Microsoft\Internet Explorer\Main,Default_Page_URL = http://ie.redirect.hp.com/...
R1 - HKLM\Software\Microsoft\Internet Explorer\Main,Default_Search_URL = http://go.microsoft.com/fwlink/?LinkId=54896
R1 - HKLM\Software\Microsoft\Internet Explorer\Main,Search Page = https://www.bing.com/?toHttps=1&redig=5FC791212101479BAFBE1A679848B1AF
R0 - HKLM\Software\Microsoft\Internet Explorer\Main,Start Page = http://ie.redirect.hp.com/...
R0 - HKLM\Software\Microsoft\Internet Explorer\Search,SearchAssistant =
R0 - HKLM\Software\Microsoft\Internet Explorer\Search,CustomizeSearch =
R0 - HKCU\Software\Microsoft\Internet Explorer\Toolbar,LinksFolderName =
R3 - URLSearchHook: Yahoo! Toolbar avec bloqueur de fenêtres pop-up - {EF99BD32-C1FB-11D2-892F-0090271D4F88} - (no file)
O1 - Hosts: ::1 localhost
O2 - BHO: Aide pour le lien d'Adobe PDF Reader - {06849E9F-C8D7-4D59-B87D-784B7D6BE0B3} - C:\Program Files\Common Files\Adobe\Acrobat\ActiveX\AcroIEHelper.dll
O2 - BHO: (no name) - {1E8A6170-7264-4D0F-BEAE-D42A53123C75} - c:\Program Files\Common Files\Symantec Shared\coShared\Browser\1.5\NppBho.dll
O2 - BHO: (no name) - {3CA2F312-6F6E-4B53-A66E-4E65E497C8C0} - (no file)
O2 - BHO: SSVHelper Class - {761497BB-D6F0-462C-B6EB-D4DAF1D92D43} - C:\Program Files\Java\jre1.6.0_07\bin\ssv.dll
O2 - BHO: (no name) - {7E853D72-626A-48EC-A868-BA8D5E23E045} - (no file)
O2 - BHO: Programme d'aide de l'Assistant de connexion Windows Live - {9030D464-4C02-4ABF-8ECC-5164760863C6} - C:\Program Files\Common Files\Microsoft Shared\Windows Live\WindowsLiveLogin.dll
O2 - BHO: Google Toolbar Helper - {AA58ED58-01DD-4d91-8333-CF10577473F7} - c:\program files\google\googletoolbar2.dll
O3 - Toolbar: Show Norton Toolbar - {90222687-F593-4738-B738-FBEE9C7B26DF} - c:\Program Files\Common Files\Symantec Shared\coShared\Browser\1.5\UIBHO.dll
O3 - Toolbar: &Google - {2318C2B1-4965-11d4-9B18-009027A5CD4F} - c:\program files\google\googletoolbar2.dll
O4 - HKLM\..\Run: [Adobe Reader Speed Launcher] "C:\Program Files\Adobe\Reader 8.0\Reader\Reader_sl.exe"
O4 - HKLM\..\Run: [Symantec PIF AlertEng] "C:\Program Files\Common Files\Symantec Shared\PIF\{B8E1DD85-8582-4c61-B58F-2F227FCA9A08}\PIFSvc.exe" /a /m "C:\Program Files\Common Files\Symantec Shared\PIF\{B8E1DD85-8582-4c61-B58F-2F227FCA9A08}\AlertEng.dll"
O4 - HKLM\..\Run: [avgnt] "C:\Program Files\Avira\AntiVir PersonalEdition Classic\avgnt.exe" /min
O4 - HKCU\..\Run: [WMPNSCFG] C:\Program Files\Windows Media Player\WMPNSCFG.exe
O4 - HKCU\..\Run: [ccleaner] "C:\Program Files\CCleaner\CCleaner.exe" /AUTO
O4 - HKCU\..\Run: [msnmsgr] "C:\Program Files\Windows Live\Messenger\msnmsgr.exe" /background
O4 - HKCU\..\RunServices: [WIndows Update] C:\WINDOWS\system32\winlogonws.exe
O4 - HKUS\S-1-5-19\..\Run: [Sidebar] %ProgramFiles%\Windows Sidebar\Sidebar.exe /detectMem (User 'SERVICE LOCAL')
O4 - HKUS\S-1-5-19\..\Run: [WindowsWelcomeCenter] rundll32.exe oobefldr.dll,ShowWelcomeCenter (User 'SERVICE LOCAL')
O4 - HKUS\S-1-5-20\..\Run: [Sidebar] %ProgramFiles%\Windows Sidebar\Sidebar.exe /detectMem (User 'SERVICE RÉSEAU')
O9 - Extra button: (no name) - {08B0E5C0-4FCB-11CF-AAA5-00401C608501} - C:\PROGRA~1\Java\JRE16~4.0_0\bin\ssv.dll
O9 - Extra 'Tools' menuitem: Console Java (Sun) - {08B0E5C0-4FCB-11CF-AAA5-00401C608501} - C:\PROGRA~1\Java\JRE16~4.0_0\bin\ssv.dll
O13 - Gopher Prefix:
O15 - Trusted Zone: *.line6.net
O16 - DPF: {BDBDE413-7B1C-4C68-A8FF-C5B2B4090876} (F-Secure Online Scanner 3.3) - http://www.securitoo.com/ols/fscax.cab
O23 - Service: Planificateur Avira AntiVir Personal - Free Antivirus (AntiVirScheduler) - Avira GmbH - C:\Program Files\Avira\AntiVir PersonalEdition Classic\sched.exe
O23 - Service: Avira AntiVir Personal - Free Antivirus Guard (AntiVirService) - Avira GmbH - C:\Program Files\Avira\AntiVir PersonalEdition Classic\avguard.exe
O23 - Service: Symantec Event Manager (ccEvtMgr) - Symantec Corporation - c:\Program Files\Common Files\Symantec Shared\ccSvcHst.exe
O23 - Service: Symantec Settings Manager (ccSetMgr) - Symantec Corporation - c:\Program Files\Common Files\Symantec Shared\ccSvcHst.exe
O23 - Service: Symantec Lic NetConnect service (CLTNetCnService) - Symantec Corporation - c:\Program Files\Common Files\Symantec Shared\ccSvcHst.exe
O23 - Service: COM Host (comHost) - Symantec Corporation - c:\Program Files\Common Files\Symantec Shared\VAScanner\comHost.exe
O23 - Service: Google Updater Service (gusvc) - Google - C:\Program Files\Google\Common\Google Updater\GoogleUpdaterService.exe
O23 - Service: HP Health Check Service - Hewlett-Packard - c:\Program Files\Hewlett-Packard\HP Health Check\hphc_service.exe
O23 - Service: HP Chasis Button Service (HPBtnSrv) - Unknown owner - c:\hp\HPEZBTN\HPBtnSrv.exe
O23 - Service: InstallDriver Table Manager (IDriverT) - Macrovision Corporation - c:\Program Files\Common Files\InstallShield\Driver\1050\Intel 32\IDriverT.exe
O23 - Service: Symantec IS Password Validation (ISPwdSvc) - Symantec Corporation - c:\Program Files\Norton Internet Security\isPwdSvc.exe
O23 - Service: LightScribeService Direct Disc Labeling Service (LightScribeService) - Hewlett-Packard Company - c:\Program Files\Common Files\LightScribe\LSSrvc.exe
O23 - Service: LiveUpdate - Symantec Corporation - C:\PROGRA~1\Symantec\LIVEUP~1\LUCOMS~1.EXE
O23 - Service: LiveUpdate Notice Service Ex (LiveUpdate Notice Ex) - Symantec Corporation - c:\Program Files\Common Files\Symantec Shared\ccSvcHst.exe
O23 - Service: LiveUpdate Notice Service - Symantec Corporation - C:\Program Files\Common Files\Symantec Shared\PIF\{B8E1DD85-8582-4c61-B58F-2F227FCA9A08}\PIFSvc.exe
O23 - Service: Planificateur LiveUpdate automatique - Symantec Corporation - C:\Program Files\Symantec\LiveUpdate\ALUSchedulerSvc.exe
O23 - Service: RoxMediaDB9 - Sonic Solutions - c:\Program Files\Common Files\Roxio Shared\9.0\SharedCOM\RoxMediaDB9.exe
O23 - Service: stllssvr - MicroVision Development, Inc. - c:\Program Files\Common Files\SureThing Shared\stllssvr.exe
O23 - Service: Symantec Core LC - Unknown owner - C:\Program Files\Common Files\Symantec Shared\CCPD-LC\symlcsvc.exe
O23 - Service: Symantec AppCore Service (SymAppCore) - Symantec Corporation - c:\Program Files\Common Files\Symantec Shared\AppCore\AppSvc32.exe

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End of file - 7184 bytes

Je me demande si je n'ai pas un virus ou quelque chose du genre, si quelqu'un peut m'aider...
Merci d'avance

Configuration: Windows Vista
Firefox 3.0.4