Replying to PayPal account hacked.

so i just went to check if i had recieved a refund from a fellow NSer and saw that there was an attempt to transfer 300 dollars from my bank account to my PayPal that happened earlier today. so i basically freaked and called paypal and had them freeze the account and mark the withdrawl as unauthorized. tomorrow im going to call my bank and have them freeze that account as well untill this is all figured out.

im pretty sure this is all because my computer recently ended up with some sort of spyware trojan or virus and the only way i know this is because when i would log on to any sites that required a password they would show a page that said my computer seemed as if it was infected and it wouldnt let me on.

so basically what do i do from here? any free way to clean out my computer because im on the verge of entirely wiping everything from this piece of shit.

greatly appreciate any help.