How did he "wipe your drive clean"? If all he had to do was replace your optical drive, why aren't all your programs still on the computer? Sounds like he probably reinstalled XP himself after "wiping your drive clean" and did something wrong. May have installed the optical drive improperly or otherwise messed with your hardware.
Reinstalling XP may help if a copy or restore disk came with your computer. You can look your computer up on the manufacturer's web-site (
http://h10025.www1.hp.com/ewfrf/wc/swPfinder?query=presario+6000&tool=softwareCategory&lc=en&cc=us&dlc=en) to see what drivers may need to be downloaded / installed for your computer's built-in hardware if you're not using a factory restore disk that already includes the drivers. Doesn't look like you have too much to lose in giving it a try.
In any case, if the computer worked better when you brought it in than it did when you took it home... this computer repair guy is obviously a quack and a crook. Consider contacting the Better Business Bureau or small claims court if a substantial amount of money was involved (above the price of the new drive which will probably work if installed correctly).
If reinstalling Windows XP doesn't work, or is more than you want to do.... You'll probably have to take it to someone else. Maybe you'll be able to get in writing what the first guy did wrong. Might help you get a refund. I agree with Flame. If XP was installed and working when you brought the machine in... the quack certainly owes you a copy of XP installed and WORKING on your machine. I'd still go elsewhere for repairs to prevent any more damage from being done. If you end up having to pay for XP to be reinstalled... add it to the quack's bill. It actually might be best to take it straight to someone else without trying to reinstall XP yourself. That way, you couldn't possibly be to blame for anything the new repair shop finds wrong.
Sorry to hear about this problem you're having. Nothing worse than the feeling of being so blatantly ripped-off!!! Happened to me more than once.