Some possible consequences are a Crypto-type attack (encrypt your files and those of any computer connected via a network, pay them for the unlock key), or a keylogger may get installed which will record your keystrokes and report back to mothership. Your keystrokes may well include passwords and banking details. It may become a so-called Zombie PC, which has a piece of software installed on it through the scam which will lie dormant until activated by the scammers or anyone to whom they've sold their Zombie list. Your PC could then become part of a DDoS attack (flood a website with so many requests it can't cope and falls over), or it could be used to send out millions of scam emails.