Virus méchant détecté !

Um vírus récalcitrant resiste et danifie mon ordinateur :
Voici hijackthis :

ogfile of Trend Micro HijackThis v2.0.5
Scan saved at 12:55:16, on 22/03/2014
Platform: Windows 7 SP1 (WinNT 6.00.3505)
MSIE: Internet Explorer v11.0 (11.00.9600.16521)

FIREFOX: 16.0.1 (en-US)
Boot mode: Normal

Running processes:
C:\Program Files (x86)\Common Files\LightScribe\LightScribeControlPanel.exe
C:\Program Files (x86)\Hewlett-Packard\HP Quick Launch\HPMSGSVC.exe
C:\Windows\SysWOW64\RunDll32.exe
C:\Program Files\AVAST Software\Avast\AvastUI.exe
C:\Program Files (x86)\CyberLink\YouCam\YCMMirage.exe
C:\Program Files (x86)\Internet Explorer\IELowutil.exe
C:\Program Files (x86)\Internet Explorer\IEXPLORE.EXE
C:\Program Files (x86)\Internet Explorer\IEXPLORE.EXE
C:\Users\Microsoft\Downloads\HijackThis.exe
C:\Users\Microsoft\Downloads\HijackThis (1).exe

R1 - HKCU\Software\Microsoft\Internet Explorer\Main,Search Page = http://go.microsoft.com/fwlink/?LinkId=54896
R0 - HKCU\Software\Microsoft\Internet Explorer\Main,Start Page = https://www.google.com.br/
R0 - HKLM\Software\Microsoft\Internet Explorer\Search,SearchAssistant =
R0 - HKLM\Software\Microsoft\Internet Explorer\Search,CustomizeSearch =
R0 - HKLM\Software\Microsoft\Internet Explorer\Main,Local Page = C:\Windows\SysWOW64\blank.htm
R0 - HKCU\Software\Microsoft\Internet Explorer\Toolbar,LinksFolderName =
F2 - REG:system.ini: UserInit=userinit.exe,
O2 - BHO: AcroIEHelperStub - {18DF081C-E8AD-4283-A596-FA578C2EBDC3} - C:\Program Files (x86)\Common Files\Adobe\Acrobat\ActiveX\AcroIEHelperShim.dll
O2 - BHO: Groove GFS Browser Helper - {72853161-30C5-4D22-B7F9-0BBC1D38A37E} - C:\Program Files (x86)\Microsoft Office\Office12\GrooveShellExtensions.dll
O2 - BHO: Java(tm) Plug-In SSV Helper - {761497BB-D6F0-462C-B6EB-D4DAF1D92D43} - C:\Program Files (x86)\Java\jre6\bin\ssv.dll
O2 - BHO: avast! Online Security - {8E5E2654-AD2D-48bf-AC2D-D17F00898D06} - C:\Program Files\AVAST Software\Avast\aswWebRepIE.dll
O2 - BHO: Auxiliar de Conexão do Windows Live ID - {9030D464-4C02-4ABF-8ECC-5164760863C6} - C:\Program Files (x86)\Common Files\Microsoft Shared\Windows Live\WindowsLiveLogin.dll
O2 - BHO: Google Toolbar Helper - {AA58ED58-01DD-4d91-8333-CF10577473F7} - C:\Program Files (x86)\Google\Google Toolbar\GoogleToolbar_32.dll
O2 - BHO: Java(tm) Plug-In 2 SSV Helper - {DBC80044-A445-435b-BC74-9C25C1C588A9} - C:\Program Files (x86)\Java\jre6\bin\jp2ssv.dll
O3 - Toolbar: Google Toolbar - {2318C2B1-4965-11d4-9B18-009027A5CD4F} - C:\Program Files (x86)\Google\Google Toolbar\GoogleToolbar_32.dll
O3 - Toolbar: avast! Online Security - {CC1A175A-E45B-41ED-A30C-C9B1D7A0C02F} - C:\Program Files\AVAST Software\Avast\aswWebRepIE.dll


et le log de l'antivirus :

Database version: v2014.03.22.06

Windows 7 Service Pack 1 x64 NTFS
Internet Explorer 11.0.9600.16521
Microsoft :: MICROSOFT-HP [administrator]

23/03/2014 08:59:35
MBAM-log-2014-03-23 (09-04-33).txt

Scan type: Quick scan
Scan options enabled: Memory | Startup | Registry | File System | Heuristics/Extra | Heuristics/Shuriken | PUP | PUM
Scan options disabled: P2P
Objects scanned: 216820
Time elapsed: 4 minute(s), 37 second(s)

Memory Processes Detected: 0
(No malicious items detected)

Memory Modules Detected: 0
(No malicious items detected)

Registry Keys Detected: 1
HKCU\Software\AppDataLow\Software\Plus-HD-1.3 (PUP.Optional.PlusHD.A) -> No action taken.

Registry Values Detected: 0
(No malicious items detected)

Registry Data Items Detected: 0
(No malicious items detected)

D'avance un grand merci pour l'aide !