Downloaded a keygen for a program, but when i "sweeped" it with SpySweeper, it came up as a "mal/packer" virus. I've heard that keygens are often mis-swept for viri.

Worth worrying about?

Also, if malware is mainly for like... internet security and stuff, what's the harm/is there harm in installing it on a non-internet computer?
Yep keygens can't be trusted now. Although it is true that most keygens are often identified as a virus due to an increasingly stricter virus database rule, most of them can't be trusted. I would rather go on the net and find a key.
I know a site that gives free keys without any virus's, but you can't have it, or the mods will ban me or something.