Whish security suite are you running now though? Did you make sure to completely remove the last ones, having more than one antivirus on the go can really throw a spanner in the works. If it's only your CD-drive though, it's far more likely to be a knackered motherboard or corrupt BIOS, might even be worth giving your IDE/SATA cables a wobble around, check everything's stuck in straight and in the right place. If you've got another CD drive hanging around somwhere, fit that in place of your current one and see if the problem's still there, and even then you can try shifting it to an older computer to see if it's just a hardware compatibility issue of some kind. Doing an over-the-top windows installation could help, and definitely check the stability of your RAM in it's sockets. It might just be age, most home PCs last about three or four years and yours does sound like a hardware error.
Bleh, sorry that's a bit garbled, just typed it out as I thoguh of things, but hopefully one of those'll be helpful. Good luck!