Popup intempestif

Bonjour, j'ai besoin d'aide.
Depuis quelques jour, un popup "sécurité" de ma barre tache apparait de manière intempestive,
m'indiquant "You have a security problem!". De plus, de temps à autre, une page internet s'ouvre,
me montrant un scan bizarre d'un poste de travail. Le processus correspondant est ~tmpc.

Je voudrais savoir comment enlever ça de mon ordi. je vous ai joint le rapport hijackthis.
J'espère que quelqu'un pourra m'aider.

Logfile of Trend Micro HijackThis v2.0.2
Scan saved at 16:27:50, on 17/12/2008
Platform: Windows XP SP3 (WinNT 5.01.2600)
MSIE: Internet Explorer v7.00 (7.00.6000.16762)
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\Explorer.EXE
C:\WINDOWS\system32\ctfmon.exe
C:\WINDOWS\system32\spoolsv.exe
C:\Program Files\Avira\AntiVir PersonalEdition Classic\sched.exe
C:\WINDOWS\system32\RUNDLL32.EXE
C:\WINDOWS\SOUNDMAN.EXE
C:\Program Files\Avira\AntiVir PersonalEdition Classic\avgnt.exe
C:\Program Files\Adobe\Reader 8.0\Reader\Reader_sl.exe
C:\Program Files\DAEMON Tools Lite\daemon.exe
C:\Program Files\Common Files\Ahead\Lib\NMBgMonitor.exe
C:\Program Files\DNA\btdna.exe
C:\DOCUME~1\Benjamin\LOCALS~1\Temp\yyy11321.exe
C:\Sun\SDK\jdk\bin\javaw.exe
C:\DOCUME~1\Benjamin\LOCALS~1\Temp\7C.tmp.exe
C:\WINDOWS\system32\ctfmon.exe
C:\Program Files\Common Files\Ahead\Lib\NMIndexStoreSvr.exe
C:\DOCUME~1\Benjamin\LOCALS~1\Temp\~tmpc.exe
C:\Program Files\Avira\AntiVir PersonalEdition Classic\avguard.exe
C:\Program Files\MATLAB71\webserver\bin\win32\matlabserver.exe
C:\WINDOWS\system32\nvsvc32.exe
C:\WINDOWS\System32\svchost.exe
C:\WINDOWS\system32\wuauclt.exe
C:\Documents and Settings\Benjamin\Desktop\HiJackThis.exe

R0 - HKCU\Software\Microsoft\Internet Explorer\Main,Start Page = https://www.msn.com/fr-fr/?ocid=iehp
R1 - HKLM\Software\Microsoft\Internet Explorer\Main,Default_Page_URL = https://www.msn.com/fr-fr/?ocid=iehp
R1 - HKLM\Software\Microsoft\Internet Explorer\Main,Default_Search_URL = https://www.bing.com/?toHttps=1&redig=5FC791212101479BAFBE1A679848B1AF
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 Connection Wizard,ShellNext = https://www.avast.com/store?verb=register-home&amp%3Blang=fre
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: gootbl2 - {435ADC46-DCAB-4593-92C8-25D2BEFCEAB7} - C:\WINDOWS\system32\mopona.dll (file missing)
O2 - BHO: XML module - {500BCA15-57A7-4eaf-8143-8C619470B13D} - C:\WINDOWS\system32\msxml71.dll
O2 - BHO: (no name) - {7E853D72-626A-48EC-A868-BA8D5E23E045} - (no file)
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: [SoundMan] SOUNDMAN.EXE
O4 - HKLM\..\Run: [NeroFilterCheck] C:\Program Files\Common Files\Ahead\Lib\NeroCheck.exe
O4 - HKLM\..\Run: [avgnt] "C:\Program Files\Avira\AntiVir PersonalEdition Classic\avgnt.exe" /min
O4 - HKLM\..\Run: [Adobe Reader Speed Launcher] "C:\Program Files\Adobe\Reader 8.0\Reader\Reader_sl.exe"
O4 - HKCU\..\Run: [CTFMON.EXE] C:\WINDOWS\system32\ctfmon.exe
O4 - HKCU\..\Run: [DAEMON Tools Lite] "C:\Program Files\DAEMON Tools Lite\daemon.exe" -autorun
O4 - HKCU\..\Run: [BgMonitor_{79662E04-7C6C-4d9f-84C7-88D8A56B10AA}] "C:\Program Files\Common Files\Ahead\Lib\NMBgMonitor.exe"
O4 - HKCU\..\Run: [BitTorrent DNA] "C:\Program Files\DNA\btdna.exe"
O4 - HKCU\..\Run: [Cognac] C:\DOCUME~1\Benjamin\LOCALS~1\Temp\7C.tmp.exe
O4 - HKCU\..\Run: [MSFox] C:\DOCUME~1\Benjamin\LOCALS~1\Temp\yyy11321.exe
O4 - HKUS\S-1-5-19\..\Run: [CTFMON.EXE] C:\WINDOWS\system32\CTFMON.EXE (User 'LOCAL SERVICE')
O4 - HKUS\S-1-5-20\..\Run: [CTFMON.EXE] C:\WINDOWS\system32\CTFMON.EXE (User 'NETWORK SERVICE')
O4 - HKUS\S-1-5-18\..\Run: [CTFMON.EXE] C:\WINDOWS\system32\CTFMON.EXE (User 'SYSTEM')
O4 - HKUS\.DEFAULT\..\Run: [CTFMON.EXE] C:\WINDOWS\system32\CTFMON.EXE (User 'Default user')
O4 - Startup: SDK Tray Menu.lnk = ?
O8 - Extra context menu item: E&xporter vers Microsoft Excel - res://C:\PROGRA~1\MICROS~2\Office12\EXCEL.EXE/3000
O9 - Extra button: Research - {92780B25-18CC-41C8-B9BE-3C9C571A8263} - C:\PROGRA~1\MICROS~2\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
O23 - Service: Avira AntiVir Personal - Free Antivirus Scheduler (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: InstallDriver Table Manager (IDriverT) - Macrovision Corporation - C:\Program Files\Common Files\InstallShield\Driver\11\Intel 32\IDriverT.exe
O23 - Service: MATLAB Server (matlabserver) - Unknown owner - C:\Program Files\MATLAB71\webserver\bin\win32\matlabserver.exe
O23 - Service: NBService - Nero AG - C:\Program Files\Nero\Nero 7\Nero BackItUp\NBService.exe
O23 - Service: NVIDIA Display Driver Service (NVSvc) - NVIDIA Corporation - C:\WINDOWS\system32\nvsvc32.exe

--
End of file - 5625 bytes

Configuration: Windows XP
Firefox 3.0.4