Do you mean your hard drive from your old to be put into a new?
It most likely won't boot. And, in order to "FIX" it, you need an XP cd - which you say you don't have. You also need your product key from the old machine.
You need to borrow an OEM Home version (or Pro - if that's what you had). When you find one to borrow, and after you install the hd in the new, restart - go up into the BIOS and make sure the boot priority has the cd drive first - pop in the cd - boot to it - hit Enter at the first Repair screen - hit R at the second Repair screen. DO NOT BOOT TO THE CD the next two restarts.
You most likely will have to call MS to activate - which shouldn't take more than 10-15 minutes. Tell them your old HP died, and give them the product #. It won't be a problem.