Hi,
what Win do you have ?
Is you Avast uptodate ?
Where exactly was the Trojan found (Full pathname, filename + file extension) ?
-Try using OnlineScanners , e.g. from Trendonline, Kaspersky, RAVAntivirus to get a more specific detection/Name, and then look up the Virus Info/Removal Instructions in their respective databases..
- you might also want to read the Board topics on Blaster/Lovsan worm; could be that one, too