Some threats are harmless to Windows but a big problem in other platforms. Is Avast! able to detect any of those?
Two I have recently become aware of are mentioned at http://darkfader.net/ds/. When I looked at Kaspersky’s threat list, it seems quite a few AV programs can detect these specific threats.
Since I might be getting a Sony PSP too, that might give me more non-Windows threats to contend with.