Well, I'm building a new PC, and I have all the parts selected and everything, but the only thing that remains is the OS. I went around newegg, and saw that a windows home xp with sp2 is about $189, and with all new pc, im gonna be a little short on money. So I was wondering if I could use my old computers OS, its a Windows Home XP with SP1, with the product unregistered online. The only problem is that I don't have the installation disc, but I can get one somewhere if I can use it. So can I or can I not still use the it? If I can, do I have to find the exact type thats installed on my old pc?