I've run a boot time scan and these are the results;
File C:\Documents and Settings\K\Local Settings\Temp\orz.exe\[Embedded#02270]\[Embedded#11070] is infected by Win32:Trojan-gen {Other}, Moved to chest
File C:\Documents and Settings\K\Local Settings\Temporary Internet Files\Content.IE5\U4JMXPOC\ms[2].exe\[Embedded#02270]\[Embedded#11070] is infected by Win32:Trojan-gen {Other}, Moved to chest
File C:\System Volume Information\_restore{202550A8-7A33-4BCA-9586-051D24DDBF8F}\RP142\A0041922.exe is infected by Win32:Trojan-gen {Other}, Moved to chest
File C:\WINDOWS\svchost.exe is infected by Win32:Trojan-gen {Other}, Moved to chest
File C:\WINDOWS\system32\atlcom655_84.dll\[Embedded#11070] is infected by Win32:Trojan-gen {Other}, Moved to chest
Number of searched folders: 8332
Number of tested files: 455805
Number of infected files: 5
Since I've done this I haven't received the avast! virus warning. (When I logged on this evening I received it over a dozen times.)
Nevertheless, I'm still going to follow your recommendation and download the scanners you listed.
Any information on what these files being infected means would be appreciated.