PC infecté?

Bonjour,
Voilà depuis quelques jours mon pc se comporte bizarrement. Lorsque je l'allume et je vais sur firefox (la même chose avec n'iporte quel autre navigateur), rien ne s'affiche. Si je redémarre tout va très bien.
Je ne sais pas si c'est un problème de virus.
Je vous colle mon rapport hijackthis:

Logfile of Trend Micro HijackThis v2.0.2
Scan saved at 15:10:01, on 04/06/2009
Platform: Windows XP SP3 (WinNT 5.01.2600)
MSIE: Internet Explorer v8.00 (8.00.6001.18702)
Boot mode: Normal

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\svchost.exe
C:\WINDOWS\System32\svchost.exe
C:\WINDOWS\system32\svchost.exe
C:\WINDOWS\system32\ZoneLabs\vsmon.exe
C:\WINDOWS\Explorer.EXE
C:\WINDOWS\System32\wltrysvc.exe
C:\WINDOWS\System32\bcmwltry.exe
C:\WINDOWS\system32\spoolsv.exe
C:\Program Files\Avira\AntiVir Desktop\sched.exe
C:\Program Files\Avira\AntiVir Desktop\avguard.exe
C:\WINDOWS\System32\svchost.exe
C:\Program Files\Avira\AntiVir Desktop\avmailc.exe
C:\Program Files\Avira\AntiVir Desktop\AVWEBGRD.EXE
C:\Program Files\Zone Labs\ZoneAlarm\zlclient.exe
C:\Program Files\Avira\AntiVir Desktop\avgnt.exe
C:\Program Files\Mozilla Firefox\firefox.exe
C:\Documents and Settings\Stefan\Desktop\HiJackThis.exe

R0 - HKCU\Software\Microsoft\Internet Explorer\Main,Start Page = https://www.google.fr/?gws_rd=ssl
R1 - HKLM\Software\Microsoft\Internet Explorer\Main,Default_Page_URL = http://go.microsoft.com/fwlink/?LinkId=69157
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 = about:blank
R1 - HKCU\Software\Microsoft\Windows\CurrentVersion\Internet Settings,ProxyOverride = *.local
O2 - BHO: AcroIEHelperStub - {18DF081C-E8AD-4283-A596-FA578C2EBDC3} - C:\Program Files\Common Files\Adobe\Acrobat\ActiveX\AcroIEHelperShim.dll
O2 - BHO: RealPlayer Download and Record Plugin for Internet Explorer - {3049C3E9-B461-4BC5-8870-4C09146192CA} - C:\Program Files\Real\RealPlayer\rpbrowserrecordplugin.dll
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: WOT Helper - {C920E44A-7F78-4E64-BDD7-A57026E7FEB7} - C:\Program Files\WOT\WOT.dll
O2 - BHO: Java(tm) Plug-In 2 SSV Helper - {DBC80044-A445-435b-BC74-9C25C1C588A9} - C:\Program Files\Java\jre6\bin\jp2ssv.dll
O2 - BHO: JQSIEStartDetectorImpl - {E7E6F031-17CE-4C07-BC86-EABFE594F69C} - C:\Program Files\Java\jre6\lib\deploy\jqs\ie\jqs_plugin.dll
O3 - Toolbar: WOT - {71576546-354D-41c9-AAE8-31F2EC22BF0D} - C:\Program Files\WOT\WOT.dll
O4 - HKLM\..\Run: [SiSPower] Rundll32.exe SiSPower.dll,ModeAgent
O4 - HKLM\..\Run: [ZoneAlarm Client] "C:\Program Files\Zone Labs\ZoneAlarm\zlclient.exe"
O4 - HKLM\..\Run: [avgnt] "C:\Program Files\Avira\AntiVir Desktop\avgnt.exe" /min
O8 - Extra context menu item: Add to Google Photos Screensa&ver - res://C:\WINDOWS\system32\GPhotos.scr/200
O8 - Extra context menu item: E&xporter vers Microsoft Excel - res://C:\PROGRA~1\MICROS~4\Office12\EXCEL.EXE/3000
O9 - Extra button: Envoyer à OneNote - {2670000A-7350-4f3c-8081-5663EE0C6C49} - C:\PROGRA~1\MICROS~4\Office12\ONBttnIE.dll
O9 - Extra 'Tools' menuitem: &Envoyer à OneNote - {2670000A-7350-4f3c-8081-5663EE0C6C49} - C:\PROGRA~1\MICROS~4\Office12\ONBttnIE.dll
O9 - Extra button: Research - {92780B25-18CC-41C8-B9BE-3C9C571A8263} - C:\PROGRA~1\MICROS~4\Office12\REFIEBAR.DLL
O9 - Extra button: (no name) - {e2e2dd38-d088-4134-82b7-f2ba38496583} - C:\WINDOWS\Network Diagnostic\xpnetdiag.exe
O9 - Extra 'Tools' menuitem: @xpsp3res.dll,-20001 - {e2e2dd38-d088-4134-82b7-f2ba38496583} - C:\WINDOWS\Network Diagnostic\xpnetdiag.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
O16 - DPF: {30528230-99f7-4bb4-88d8-fa1d4f56a2ab} (Installation Support) - C:\Program Files\Yahoo!\Common\Yinsthelper.dll
O17 - HKLM\System\CCS\Services\Tcpip\..\{AD1BEBEE-F565-4940-A66B-C5DC8988E7EF}: NameServer = 193.138.196.240,193.231.104.2,193.231.107.2
O18 - Protocol: wot - {C2A44D6B-CB9F-4663-88A6-DF2F26E4D952} - C:\Program Files\WOT\WOT.dll
O23 - Service: Avira AntiVir MailGuard (AntiVirMailService) - Avira GmbH - C:\Program Files\Avira\AntiVir Desktop\avmailc.exe
O23 - Service: Avira AntiVir Planificateur (AntiVirSchedulerService) - Avira GmbH - C:\Program Files\Avira\AntiVir Desktop\sched.exe
O23 - Service: Avira AntiVir Guard (AntiVirService) - Avira GmbH - C:\Program Files\Avira\AntiVir Desktop\avguard.exe
O23 - Service: Avira AntiVir WebGuard (AntiVirWebService) - Avira GmbH - C:\Program Files\Avira\AntiVir Desktop\AVWEBGRD.EXE
O23 - Service: Google Software Updater (gusvc) - Google - C:\Program Files\Google\Common\Google Updater\GoogleUpdaterService.exe
O23 - Service: InstallDriver Table Manager (IDriverT) - Macrovision Corporation - C:\Program Files\Common Files\InstallShield\Driver\1150\Intel 32\IDriverT.exe
O23 - Service: ServiceLayer - Nokia. - C:\Program Files\PC Connectivity Solution\ServiceLayer.exe
O23 - Service: TuneUp Drive Defrag Service (TuneUp.Defrag) - TuneUp Software - C:\WINDOWS\System32\TuneUpDefragService.exe
O23 - Service: TrueVector Internet Monitor (vsmon) - Zone Labs, LLC - C:\WINDOWS\system32\ZoneLabs\vsmon.exe
O23 - Service: Broadcom Wireless LAN Tray Service (wltrysvc) - Unknown owner - C:\WINDOWS\System32\wltrysvc.exe