TrojanDownloader.Win32.Agent.j  virus!

I’ve been finding solutions on this site for some time, but this is the first time I’ve posted for help.  I’m working on a computer that was totally infected with spyware and viruses.  It is XP Home and is now up to date with all service packs, anti-spyware tools and anti-virus software.  I’ve cleaned up all the spyware and viruses except for one remaining one that I can’t get rid of.  It is detected in memory by Kaspersky and Antiy Ghost as  TrojanDownloader.Win32.Agent.j  but it is not detected anywhere on the hard drive. Therefore, the file containing the infection cannot be cleaned or deleted.  Other software, such as Norton Antivirus Corporate Edition does not detect it at all.  It was originally detected in several files by AVG 6.0 and all those files were removed, but it is still showing up in memory with all startups disabled.  I might have assumed that the system was clean and that it was just a mis-detection if it wasn’t for the fact that symptoms are still showing up.  The start and search pages are constantly changing.  The virus still shows up in memory even when booting into safe mode, so it is something that is not easily disabled by just removing it from startup.  It must be loading as a dll required by some system device that is needed even in safe mode.  It is not loading as a task or a process that can be killed either.  It shows up in memory as a loaded dll module with a location of “c:\windows\system32\logphip.dll”  but on the hard drive, no such file exists.  I’ve run updated versions of AdAware, Spybot, SpySweeper, AVG 6.0, CW Shredder, and HijackThis, and have removed everything that is suspicious. Below is the current log from HijackThis.  Notice the entries for the search pages.  I’ve removed them many times, but they keep coming back….. even in safe mode. Let me know what other information I can provide.  I’m and my wits end with this one.

   Logfile of HijackThis v1.97.7
Scan saved at 3:40:11 PM, on 6/19/2004
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\ctfmon.exe
C:\Documents and Settings\Linda\Desktop\HijackThis.exe

R1 - HKCU\Software\Microsoft\Internet Explorer\Main,Search Bar = file://C:\DOCUME~1\LINDAS~1\LOCALS~1\Temp\sp.html
R1 - HKCU\Software\Microsoft\Internet Explorer\Main,Search Page = file://C:\DOCUME~1\LINDAS~1\LOCALS~1\Temp\sp.html
R1 - HKCU\Software\Microsoft\Internet Explorer\Search,SearchAssistant = file://C:\DOCUME~1\LINDAS~1\LOCALS~1\Temp\sp.html
R1 - HKLM\Software\Microsoft\Internet Explorer\Main,Search Bar = file://C:\DOCUME~1\LINDAS~1\LOCALS~1\Temp\sp.html
R1 - HKCU\Software\Microsoft\Internet Explorer\Main,HomeOldSP = about:blank
O9 - Extra button: Related (HKLM)
O9 - Extra 'Tools' menuitem: Show &Related Links (HKLM)