[grubbymitts]

what p2p program are you using - it sounds like an edonkey derivative if you have partial files. This program should move the full avi into a designated folder once it has finished downloading it and then delete any .partial files. So, I would conclude that you haven't actually finished the download and that your P2P client was fibbing (ie crashed) or the person you were leeching from was only sharing a partial file in the first place.

It is unlikely it is a virus. The problem with virus killers is they often work on an heurustic (spelling?) basis where they look for patterns inside a file that are the same as a virus. This can lead to what are known as false positives, especially with partial downloads that may have a few bytes in them that, coincidentally, are the same as a virus pattern. Once the full file is downloaded these bytes may have been changed completely or added to, making it different from the virus pattern so a normal scan would not show it as a virus then, even though it did 30 minutes before.