The last time I took my hard drive for repair the technician changed the Norton antivirus for the AVG free edition because the Norton was not doing much for me. I have found doing a virus scan that I have several infections. Here is my Hijackthis log:

Logfile of HijackThis v1.97.7
Scan saved at 9:42:50 PM, on 9/16/2006
Platform: Windows XP (WinNT 5.01.2600)
MSIE: Internet Explorer v6.00 (6.00.2600.0000)
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\spoolsv.exe
C:\PROGRA~1\Grisoft\AVGFRE~1\avgamsvr.exe
C:\PROGRA~1\Grisoft\AVGFRE~1\avgupsvc.exe
C:\Program Files\Olympus\DeviceDetector\DM1Service.exe
C:\Program Files\Messenger\msmsgs.exe
C:\Program Files\Olympus\DeviceDetector\DevDtct2.exe
C:\Program Files\Yahoo!\Messenger\ymsgr_tray.exe
C:\WINDOWS\System32\wuauclt.exe
C:\Program Files\Internet Explorer\iexplore.exe
C:\Documents and Settings\Owner\My Documents\hijack\HijackThis.exe
R1 - HKCU\Software\Microsoft\Internet Explorer\Main,Search Bar = http://us.rd.yahoo.com/customize/ie/...ch/search.html
R1 - HKCU\Software\Microsoft\Internet Explorer\Main,Search Page = http://us.rd.yahoo.com/customize/ie/.../www.yahoo.com
R0 - HKCU\Software\Microsoft\Internet Explorer\Main,Start Page = http://yahoo.com/
R1 - HKCU\Software\Microsoft\Internet Explorer\Main,Default_Page_URL = http://us6.hpwis.com/
R1 - HKCU\Software\Microsoft\Internet Explorer\Main,Default_Search_URL = http://srch-us6.hpwis.com/
R0 - HKLM\Software\Microsoft\Internet Explorer\Main,Start Page = http://us6.hpwis.com/
R1 - HKLM\Software\Microsoft\Internet Explorer\Main,Search Bar = http://us.rd.yahoo.com/customize/ie/...ch/search.html
R1 - HKLM\Software\Microsoft\Internet Explorer\Main,Search Page = http://us.rd.yahoo.com/customize/ie/.../www.yahoo.com
R1 - HKLM\Software\Microsoft\Internet Explorer\Main,Default_Page_URL = http://us6.hpwis.com/
R1 - HKLM\Software\Microsoft\Internet Explorer\Main,Default_Search_URL = http://us.rd.yahoo.com/customize/ie/.../www.yahoo.com
R0 - HKLM\Software\Microsoft\Internet Explorer\Search,CustomizeSearch = http://srch-us6.hpwis.com/
R1 - HKCU\Software\Microsoft\Internet Explorer\SearchURL,(Default) = http://us.rd.yahoo.com/customize/ie/.../www.yahoo.com
O2 - BHO: (no name) - {02478D38-C3F9-4EFB-9B51-7695ECA05670} - C:\Program Files\Yahoo!\Companion\Installs\cpn0\yt.dll
O2 - BHO: (no name) - {06849E9F-C8D7-4D59-B87D-784B7D6BE0B3} - C:\Program Files\Adobe\Acrobat 5.0\Reader\ActiveX\AcroIEHelper.ocx
O2 - BHO: (no name) - {5BAB4B5B-68BC-4B02-94D6-2FC0DE4A7897} - C:\Program Files\Yahoo!\Common\yiesrvc.dll
O2 - BHO: (no name) - {71ec7086-1bc4-41ea-8db6-2e1b3f8900e1} - C:\WINDOWS\system32\Dcacsrv.dll (file missing)
O3 - Toolbar: hp toolkit - {B2847E28-5D7D-4DEB-8B67-05D28BCF79F5} - C:\HP\EXPLOREBAR\HPTOOLKT.DLL
O3 - Toolbar: &Radio - {8E718888-423F-11D2-876E-00A0C9082467} - C:\WINDOWS\System32\msdxm.ocx
O3 - Toolbar: Yahoo! Toolbar - {EF99BD32-C1FB-11D2-892F-0090271D4F88} - C:\Program Files\Yahoo!\Companion\Installs\cpn0\yt.dll
O4 - HKLM\..\Run: [NvCplDaemon] RUNDLL32.EXE NvQTwk,NvCplDaemon initialize
O4 - HKCU\..\Run: [MSMSGS] "C:\Program Files\Messenger\msmsgs.exe" /background
O4 - HKCU\..\Run: [Yahoo! Pager] C:\Program Files\Yahoo!\Messenger\ypager.exe -quiet
O4 - Global Startup: Device Detector 2.lnk = C:\Program Files\Olympus\DeviceDetector\DevDtct2.exe
O8 - Extra context menu item: &Yahoo! Search - file:///C:\Program Files\Yahoo!\Common/ycsrch.htm
O8 - Extra context menu item: Yahoo! &Dictionary - file:///C:\Program Files\Yahoo!\Common/ycdict.htm
O8 - Extra context menu item: Yahoo! &Maps - file:///C:\Program Files\Yahoo!\Common/ycmap.htm
O8 - Extra context menu item: Yahoo! &SMS - file:///C:\Program Files\Yahoo!\Common/ycsms.htm
O9 - Extra button: Yahoo! Services (HKLM)
O9 - Extra button: Messenger (HKLM)
O9 - Extra 'Tools' menuitem: Windows Messenger (HKLM)
O12 - Plugin for .spop: C:\Program Files\Internet Explorer\Plugins\NPDocBox.dll
O16 - DPF: {30528230-99f7-4bb4-88d8-fa1d4f56a2ab} (YInstStarter Class) - C:\Program Files\Yahoo!\Common\yinsthelper.dll
O16 - DPF: {9A9307A0-7DA4-4DAF-B042-5009F29E09E1} (ActiveScan Installer Class) - http://www.pandasoftware.com/activescan/as5/asinst.cab
O16 - DPF: {B38870E4-7ECB-40DA-8C6A-595F0A5519FF} (MsnMessengerSetupDownloadControl Class) - http://messenger.msn.com/download/Ms...Downloader.cab
O16 - DPF: {D27CDB6E-AE6D-11CF-96B8-444553540000} (Shockwave Flash Object) - http://fpdownload.macromedia.com/pub...sh/swflash.cab
O17 - HKLM\System\CCS\Services\Tcpip\..\{A3A73718-7261-40D0-845C-3BC334B46D43}: NameServer = 216.67.192.3 66.133.189.215

AVG does not want to remove or it may well be I do not know how to quarantine, could you please, please help me? Thank you so much.

Your copy of HJT is outdated. Please download the latest version and post a new log: http://www.hijackthis.de/downloads/hijackthis_199.zip

Your XP is running without any Service Pack and updates/patches/hotfixes. This is not recommended. Please download SP2 and all ~100 critical updates/fixes that were released since 2004 to have them ready when your system is clean again. It may turn out to be impossible to prevent a reinfection after cleanup (if possible at all) without closing the exploited loopholes.

Have you tried running AVG in Safe Mode? Malware files can't be removed when they are running and in Safe Mode they might be not in use. (To enter Safe Mode, press <F8> after the BIOS screen on startup)