Can anyone help with a computer virus?

Does anybody know what you can do about a virus?....i turned on our family computer and this program called Malware keeps popping up and doing an automatic scan. It keeps asking for credit info...which of course i won't give....but i cannot open any programs or go online or anything. I can't even open the calculator. Absolutely nothing will open and not to mention there's this like pig squeal that screeches and the stupid pop up comes up again. Any info would help. FML