Major virus hitting all household computers

Hello,
My family has 2 computers, a desktop, and a laptop. The desktop recently went through a very odd and strange problem. The computer was turned off (as normal) and then when we tried to acres our computer file it "logged on" then imediately "logged off." we took to people, they fixed it but now the EXACT same thing is happening to the laptop. What virus did we get? And whatever it was, can we get rid of it without haveing to pay hundreds of dollars?