Do I have a new doorstop?

I have a Toshiba Satellite A55-S306. I have not added memory, installed new hardware, etc.etc. This computer has something of a sordid past. The first week I had it, before I installed adequate security software, my kids and some friends connected to our home wireless network and proceeded to download every game known to man. And every piece of spyware, every virus and everything else at the same time. I ran multiple pieces of cleanup software but was never able to get the machine to work right, so we used the recovery disks and started over.

It worked well for awhile, but then I started having problems with it suddenly shutting down. Then the machine experienced a bump - it slid from the tray table in my car onto the car floor (maybe one foot?). Since then, when I try to start it up I get a blue screen with the message "IRQL_NOT_LESS_THAN_OR_EQUAL" and a bunch of stuff about compatability issues with new hardware or software. For awhile it would go to this screen and stay, but now it sometimes just flips to it and then immediately reboots. I can sometimes start up in Safe Mode. My assistant took it to a shop and they said that the hard drive was fried/not fixable.

If someone has a better answer, great. But here's my real question. I have virtually no data on this computer about which I'm worried. I just want to have a working laptop. So would it work for me to just remove the hard drive and put in a new one? And is this as simple as it sounds - just unscrew the old one and screw in the new one? And do I then have to use the recovery disks again? Thoughts on using recovery disks from a brand new Toshiba (with Vista instead of XP)? Any thoughts would be appreciated!