AVG Anti Virus is one of the leading free (and usually quite reliable) programs that we actually suggest for people on occasion.  However today they slipped up a bit; this morning the daily update to the database suggested that of the Windows operating system files, user32.dll (a necessary file) was a potential virus.  If you have AVG, and it asks you to delete that, please don't.

More from AVG: http://freeforum.avg.com/read.php?7,155461#msg-155501