Hey puter dudes

My puter at the house is giving me a warning that it has been invaded with spyware, and recommends that I download a blocker (I don't recall the name,
I'm at work now). I don't know if this is legit or not, what should I do?? Any and all help would be greatly appreciated.
As always remember "The computer Illiterate are people too!!!"(just slower)
Thanx in advance,
Rick