Hi,
is avast updated (program & database) ?
have you done a full scan with settings changed to
Thorough scan & Archive Scanning ?
to get a second opinion and some info on removal, try other Scanners, e.g.
Trend & KAV (see below in my sig)
Spybot and Ad-Aware (DL-Links here in the board or via google)
are there references in the registry to this
/documents/winshow/winshow.dll - file ?
please also list your startup-Programs, e.g. with MSCONFIG
& the contests of the hosts or lmhosts-file(s) ->> find with Explorer-Search
Which WIN do you have ?