If you do want to rebuild, Windows7 could be an option depending on how old your Laptop is.
Download/run the Windows 7 upgrade advisor.
If you want to say with XP, then you should be able to download the drivers for your laptop (sound, video, lan, wireless, etc...) from the manufacturers site.
As for XP any matching XP CD will do (home, professional, SP2, etc...). All you need is the software key which is typically pasted somewhere on the bottom of the laptop. If you can't scare up an XP install CD, just post it here. I expect someone would be able to squirt you a copy via the intertubes. Err, you do have a CD burner right?