PC qui s'éteint tout seul

Bonjour,
Mon frère dispose d'un pc portable Acer Travelmate 2355XM, Intel Celeron, avec Windows XP. Le problème c'est qu'il s'éteint tout seul, et parfois il faut attendre longtemps jusqu'à ce que l'on puisse le rallumer.
Il fonctionne à une température "normale", loin d'être alarmante.

Voici son rapport Hijackthis :

Logfile of Trend Micro HijackThis v2.0.2
Scan saved at 18:05:02, on 03/07/2008
Platform: Windows XP SP2 (WinNT 5.01.2600)
MSIE: Internet Explorer v7.00 (7.00.6000.16674)
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:\Program Files\Alwil Software\Avast4\aswUpdSv.exe
C:\Program Files\Alwil Software\Avast4\ashServ.exe
C:\WINDOWS\system32\spoolsv.exe
C:\Acer\eManager\anbmServ.exe
C:\WINDOWS\system32\svchost.exe
C:\Program Files\Alwil Software\Avast4\ashMaiSv.exe
C:\Program Files\Alwil Software\Avast4\ashWebSv.exe
C:\WINDOWS\system32\wuauclt.exe
C:\WINDOWS\Explorer.EXE
C:\WINDOWS\system32\igfxtray.exe
C:\WINDOWS\system32\hkcmd.exe
C:\WINDOWS\SOUNDMAN.EXE
C:\WINDOWS\AGRSMMSG.exe
C:\Program Files\ltmoh\Ltmoh.exe
C:\Program Files\Synaptics\SynTP\SynTPLpr.exe
C:\Program Files\Synaptics\SynTP\SynTPEnh.exe
C:\Program Files\CyberLink\PowerDVD\PDVDServ.exe
C:\acer\epm\epm-dm.exe
C:\PROGRA~1\LAUNCH~1\LManager.EXE
C:\Program Files\Fichiers communs\Real\Update_OB\realsched.exe
C:\Program Files\QuickTime\qttask.exe
C:\PROGRA~1\ALWILS~1\Avast4\ashDisp.exe
C:\Program Files\Browser Mouse\mouse32a.exe
C:\Program Files\Java\jre1.6.0_05\bin\jusched.exe
C:\Program Files\Caere\OmniPagePro90\opware32.exe
C:\WINDOWS\system32\ctfmon.exe
C:\WINDOWS\system32\ntvdm.exe
C:\Program Files\Messenger\msmsgs.exe
C:\Program Files\Adobe\Acrobat 7.0\Reader\reader_sl.exe
C:\Program Files\SMC\SMCWUSB-G 802.11g Wireless USB 2.0 Adapter\SMCWGUTI.exe
C:\Documents and Settings\Gaëtan\Bureau\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 = 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
R0 - HKCU\Software\Microsoft\Internet Explorer\Toolbar,LinksFolderName = Liens
O2 - BHO: Adobe PDF Reader Link Helper - {06849E9F-C8D7-4D59-B87D-784B7D6BE0B3} - C:\Program Files\Adobe\Acrobat 7.0\ActiveX\AcroIEHelper.dll
O2 - BHO: RXResultTracker Class - {59879FA4-4790-461c-A1CC-4EC4DE4CA483} - C:\Program Files\RXToolBar\sfcont.dll (file missing)
O2 - BHO: SSVHelper Class - {761497BB-D6F0-462C-B6EB-D4DAF1D92D43} - C:\Program Files\Java\jre1.6.0_05\bin\ssv.dll
O2 - BHO: Google Toolbar Helper - {AA58ED58-01DD-4d91-8333-CF10577473F7} - c:\program files\google\googletoolbar2.dll
O3 - Toolbar: Easy-WebPrint - {327C2873-E90D-4c37-AA9D-10AC9BABA46C} - C:\Program Files\Canon\Easy-WebPrint\Toolband.dll
O3 - Toolbar: &Google - {2318C2B1-4965-11d4-9B18-009027A5CD4F} - c:\program files\google\googletoolbar2.dll
O4 - HKLM\..\Run: [LaunchApp] Alaunch
O4 - HKLM\..\Run: [IgfxTray] C:\WINDOWS\system32\igfxtray.exe
O4 - HKLM\..\Run: [HotKeysCmds] C:\WINDOWS\system32\hkcmd.exe
O4 - HKLM\..\Run: [SoundMan] SOUNDMAN.EXE
O4 - HKLM\..\Run: [AGRSMMSG] AGRSMMSG.exe
O4 - HKLM\..\Run: [LtMoh] C:\Program Files\ltmoh\Ltmoh.exe
O4 - HKLM\..\Run: [SynTPLpr] C:\Program Files\Synaptics\SynTP\SynTPLpr.exe
O4 - HKLM\..\Run: [SynTPEnh] C:\Program Files\Synaptics\SynTP\SynTPEnh.exe
O4 - HKLM\..\Run: [RemoteControl] "C:\Program Files\CyberLink\PowerDVD\PDVDServ.exe"
O4 - HKLM\..\Run: [IMJPMIG8.1] "C:\WINDOWS\IME\imjp8_1\IMJPMIG.EXE" /Spoil /RemAdvDef /Migration32
O4 - HKLM\..\Run: [MSPY2002] C:\WINDOWS\system32\IME\PINTLGNT\ImScInst.exe /SYNC
O4 - HKLM\..\Run: [PHIME2002ASync] C:\WINDOWS\system32\IME\TINTLGNT\TINTSETP.EXE /SYNC
O4 - HKLM\..\Run: [PHIME2002A] C:\WINDOWS\system32\IME\TINTLGNT\TINTSETP.EXE /IMEName
O4 - HKLM\..\Run: [EPM-DM] c:\acer\epm\epm-dm.exe
O4 - HKLM\..\Run: [ePowerManagement] C:\Acer\ePM\ePM.exe boot
O4 - HKLM\..\Run: [LManager] C:\PROGRA~1\LAUNCH~1\LManager.EXE
O4 - HKLM\..\Run: [Easy-PrintToolBox] C:\Program Files\Canon\Easy-PrintToolBox\BJPSMAIN.EXE /logon
O4 - HKLM\..\Run: [TkBellExe] "C:\Program Files\Fichiers communs\Real\Update_OB\realsched.exe" -osboot
O4 - HKLM\..\Run: [P2P Networking] C:\WINDOWS\system32\P2P Networking\P2P Networking.exe /AUTOSTART
O4 - HKLM\..\Run: [SemanticInsight] C:\Program Files\RXToolBar\Semantic Insight\SemanticInsight.exe
O4 - HKLM\..\Run: [AltnetPointsManager] c:\program files\altnet\points manager\points manager.exe -s
O4 - HKLM\..\Run: [QuickTime Task] "C:\Program Files\QuickTime\qttask.exe" -atboottime
O4 - HKLM\..\Run: [avast!] C:\PROGRA~1\ALWILS~1\Avast4\ashDisp.exe
O4 - HKLM\..\Run: [FLMOFFICE4DMOUSE] C:\Program Files\Browser Mouse\mouse32a.exe
O4 - HKLM\..\Run: [SunJavaUpdateSched] "C:\Program Files\Java\jre1.6.0_05\bin\jusched.exe"
O4 - HKLM\..\Run: [OmniPage] C:\Program Files\Caere\OmniPagePro90\opware32.exe
O4 - HKLM\..\Run: [PDF3 Registry Controller] "C:\Program Files\ScanSoft\PDF Professional 3.0\\RegistryController.exe"
O4 - HKCU\..\Run: [CTFMON.EXE] C:\WINDOWS\system32\ctfmon.exe
O4 - HKCU\..\Run: [MSMSGS] "C:\Program Files\Messenger\msmsgs.exe" /background
O4 - HKUS\S-1-5-19\..\Run: [CTFMON.EXE] C:\WINDOWS\system32\CTFMON.EXE (User 'SERVICE LOCAL')
O4 - HKUS\S-1-5-20\..\Run: [CTFMON.EXE] C:\WINDOWS\system32\CTFMON.EXE (User 'SERVICE RÉSEAU')
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 - Global Startup: Microsoft Office.lnk = C:\Program Files\Microsoft Office\Office10\OSA.EXE
O4 - Global Startup: Adobe Gamma Loader.exe.lnk = C:\Program Files\Fichiers communs\Adobe\Calibration\Adobe Gamma Loader.exe
O4 - Global Startup: Adobe Reader Speed Launch.lnk = C:\Program Files\Adobe\Acrobat 7.0\Reader\reader_sl.exe
O4 - Global Startup: SMCWUSB-G 802.11g Wireless USB Utility.lnk = C:\Program Files\SMC\SMCWUSB-G 802.11g Wireless USB 2.0 Adapter\SMCWGUTI.exe
O8 - Extra context menu item: &Copy to clipboard - C:\\Program Files\\My piky Load\\add2.htm
O8 - Extra context menu item: E&xporter vers Microsoft Excel - res://C:\PROGRA~1\MICROS~2\Office10\EXCEL.EXE/3000
O8 - Extra context menu item: Easy-WebPrint Ajouter à la liste d'impressions - res://C:\Program Files\Canon\Easy-WebPrint\Resource.dll/RC_AddToList.html
O8 - Extra context menu item: Easy-WebPrint Impression rapide - res://C:\Program Files\Canon\Easy-WebPrint\Resource.dll/RC_HSPrint.html
O8 - Extra context menu item: Easy-WebPrint Imprimer - res://C:\Program Files\Canon\Easy-WebPrint\Resource.dll/RC_Print.html
O8 - Extra context menu item: Easy-WebPrint Prévisualiser - res://C:\Program Files\Canon\Easy-WebPrint\Resource.dll/RC_Preview.html
O8 - Extra context menu item: Ouvrir le fichier PDF dans Word (PDF Converter 3.0) - res://C:\Program Files\ScanSoft\PDF Professional 3.0\IEShellExt.dll /300
O9 - Extra button: (no name) - {08B0E5C0-4FCB-11CF-AAA5-00401C608501} - C:\Program Files\Java\jre1.6.0_05\bin\ssv.dll
O9 - Extra 'Tools' menuitem: Console Java (Sun) - {08B0E5C0-4FCB-11CF-AAA5-00401C608501} - C:\Program Files\Java\jre1.6.0_05\bin\ssv.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
O14 - IERESET.INF: START_PAGE_URL=https://www.free.fr/freebox/index.html
O16 - DPF: {1D6711C8-7154-40BB-8380-3DEA45B69CBF} (Web P2P Installer) -
O16 - DPF: {B64F4A7C-97C9-11DA-8BDE-F66BAD1E3F3A} - https://www.afternic.com/domains/errorsafe.com
O16 - DPF: {F919FBD3-A96B-4679-AF26-F551439BB5FD} - https://www.afternic.com/domains/errorsafe.com
O18 - Filter hijack: text/html - {2AB289AE-4B90-4281-B2AE-1F4BB034B647} - C:\Program Files\RXToolBar\sfcont.dll
O23 - Service: Notebook Manager Service (anbmService) - OSA Technologies Inc. - C:\Acer\eManager\anbmServ.exe
O23 - Service: avast! iAVS4 Control Service (aswUpdSv) - ALWIL Software - C:\Program Files\Alwil Software\Avast4\aswUpdSv.exe
O23 - Service: avast! Antivirus - ALWIL Software - C:\Program Files\Alwil Software\Avast4\ashServ.exe
O23 - Service: avast! Mail Scanner - ALWIL Software - C:\Program Files\Alwil Software\Avast4\ashMaiSv.exe
O23 - Service: avast! Web Scanner - ALWIL Software - C:\Program Files\Alwil Software\Avast4\ashWebSv.exe
O23 - Service: Google Updater Service (gusvc) - Google - C:\Program Files\Google\Common\Google Updater\GoogleUpdaterService.exe
O23 - Service: InstallDriver Table Manager (IDriverT) - Macrovision Corporation - C:\Program Files\Fichiers communs\InstallShield\Driver\11\Intel 32\IDriverT.exe