Which operating system are you running?
If Windows, which one?
If you have any data on the drive that you must have, transfer it off the PC & wipe the drive.
(there are milder ways to clean up there crap, but if you are not PC savy wiping it is your best bet)
That scam has been around for awhile.
They actually make your computer worse when you pay them to fix it.
Then they want more mullah.