How come every time that I download a software file it has a virus.

Heaps of program files are infected, unfortunately. At least you're scanning files & finding out that they're bad If you want to keep on trying with program files, make sure to chack the file with Bitzi before download...if other users have rated the file, you'll get some idea of it's content & quality. Make sure to be very careful with any .zip. .exe, .rar files.
How to use Bitzi

Just so that you know, even if a program file's clean there's a good chance that it won't work anyway...will need a CD or code to run.
WARNING: Viruses on the network you should be aware of