Norton Anti-virus & Drivecleaner Help!?

I recently got attacked by the virus Drivecleaner. My norton anti-virus had expired, but it kept telling me that it detected the virus and renew immediately, so i renewed and scanned my computer. Before that, I installed the spyware something(to remove the drivecleaner), and i think it got rid of the drivecleaner, b/c when i scanned with norton, the virus was gone. Im wandering if it REALLY is gone and scared to use my computer. Im very comp illiterate, and im wandering what "cookies" are....and if drivecleaner has installed bad ones on my comp that norton wont pick up on! Can someone please explain this to me!!! I dont want anyone getting my personal info when i use my comp! THANKS SO MUCH!!!