Pc très lent + pub envahissante

bonjour,
Mon pc rame de plus en plus, quelle que soit la fonction demandée (démarrage, navigation et fermeture de windows).
De plus, depuis quelques temps, il est envahit de fenêtres publicitaires et proposition de scans (drive cleaner, doctor system etc..).
je suis sous XP, pc packard bell imédia, IE 7
J ai avast, adaware et ccleaner ...

voici mon analyse hijackthis

Logfile of HijackThis v1.99.1
Scan saved at 13:14:38, on 28/02/2007
Platform: Windows XP SP2 (WinNT 5.01.2600)
MSIE: Internet Explorer v7.00 (7.00.6000.16414)

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\spoolsv.exe
C:\Apps\ActivBoard\nhksrv.exe
C:\Program Files\Alwil Software\Avast4\aswUpdSv.exe
C:\Program Files\Alwil Software\Avast4\ashServ.exe
C:\WINDOWS\system32\slserv.exe
C:\WINDOWS\System32\svchost.exe
C:\Program Files\Alwil Software\Avast4\ashMaiSv.exe
C:\Program Files\Alwil Software\Avast4\ashWebSv.exe
C:\WINDOWS\Explorer.EXE
C:\Program Files\Real\RealPlayer\RealPlay.exe
C:\PROGRA~1\ALWILS~1\Avast4\ashDisp.exe
C:\Program Files\Labtec\Labtec Mouse Software\2.0\MOUSE32A.EXE
C:\Program Files\MSN Messenger\MsnMsgr.Exe
C:\WINDOWS\system32\ctfmon.exe
C:\Program Files\Messenger\msmsgs.exe
C:\WINDOWS\System32\svchost.exe
C:\Program Files\IncrediMail\bin\IncMail.exe
C:\PROGRA~1\INCRED~1\bin\IMApp.exe
C:\Program Files\Internet Explorer\IEXPLORE.EXE
C:\Program Files\Hijackthis Version Française\VERSION TRADUITE ORIGINALE.EXE

R0 - HKCU\Software\Microsoft\Internet Explorer\Main,Start Page = https://www.orange.fr/portail
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 = https://www.msn.com/fr-fr/?ocid=iehp
R1 - HKCU\Software\Microsoft\Internet Explorer\Main,Window Title = Microsoft Internet Explorer fourni par Planetis
R0 - HKCU\Software\Microsoft\Internet Explorer\Toolbar,LinksFolderName = Liens
O4 - HKLM\..\Run: [RealTray] C:\Program Files\Real\RealPlayer\RealPlay.exe SYSTEMBOOTHIDEPLAYER
O4 - HKLM\..\Run: [avast!] C:\PROGRA~1\ALWILS~1\Avast4\ashDisp.exe
O4 - HKLM\..\Run: [LWBMOUSE] C:\Program Files\Labtec\Labtec Mouse Software\2.0\MOUSE32A.EXE
O4 - HKLM\..\Run: [UserFaultCheck] %systemroot%\system32\dumprep 0 -u
O4 - HKCU\..\Run: [MsnMsgr] "C:\Program Files\MSN Messenger\MsnMsgr.Exe" /background
O4 - HKCU\..\Run: [WOOKIT] C:\PROGRA~1\Wanadoo\Shell.exe appLaunchClientZone.shl|DEFAULT=cnx|PARAM=
O4 - HKCU\..\Run: [ctfmon.exe] C:\WINDOWS\system32\ctfmon.exe
O4 - HKCU\..\Run: [MSMSGS] "C:\Program Files\Messenger\msmsgs.exe" /background
O4 - Global Startup: Adobe Gamma Loader.exe.lnk = C:\Program Files\Fichiers communs\Adobe\Calibration\Adobe Gamma Loader.exe
O8 - Extra context menu item: E&xporter vers Microsoft Excel - res://C:\PROGRA~1\MICROS~2\Office10\EXCEL.EXE/3000
O9 - Extra button: Real.com - {CD67F990-D8E9-11d2-98FE-00C0F0318AFE} - C:\WINDOWS\System32\Shdocvw.dll
O9 - Extra button: (no name) - {e2e2dd38-d088-4134-82b7-f2ba38496583} - %windir%\Network Diagnostic\xpnetdiag.exe (file missing)
O9 - Extra 'Tools' menuitem: @xpsp3res.dll,-20001 - {e2e2dd38-d088-4134-82b7-f2ba38496583} - %windir%\Network Diagnostic\xpnetdiag.exe (file missing)
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
O11 - Options group: [INTERNATIONAL] International*
O16 - DPF: {084DAC27-6FA3-4F55-9005-033F2F102F5C} (ITPPDiagIE Class) - http://data.jeuxclassiques.com/npwwg.cab
O16 - DPF: {8E0D4DE5-3180-4024-A327-4DFAD1796A8D} (MessengerStatsClient Class) - http://messenger.zone.msn.com/binary/MessengerStatsClient.cab31267.cab
O16 - DPF: {F6BF0D00-0B2A-4A75-BF7B-F385591623AF} (Solitaire Showdown Class) - http://messenger.zone.msn.com/binary/SolitaireShowdown.cab31267.cab
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
O23 - Service: avast! iAVS4 Control Service (aswUpdSv) - Unknown owner - C:\Program Files\Alwil Software\Avast4\aswUpdSv.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: Netropa NHK Server (nhksrv) - Unknown owner - C:\Apps\ActivBoard\nhksrv.exe
O23 - Service: SmartLinkService (SLService) - - C:\WINDOWS\SYSTEM32\slserv.exe

Merci pour toute aide