I have also a problem with Trojano.
The infected files in my system (Win98) reside in c:\windows and c:\windows\system and thee are a lot of them. Avast identified 3 variants :
Win32.Trojano-173
Win32.Trojano-180
Win32.Trojano-181

Most are of the 180 type.

Effects noticed. Unusual number of popups in IE (got around by m0oving to Mozila).
At some point added a lot of startup files and the PC could not finish booting. Went around this by booting in safe-mode and removing the startups.
Up to now Avast is unable to repair the files giving the message could not process xxxxxx.
I cannot just dlelete the files because some belong to Windows And I wish to avoid reinstalling Windows.

Avi