At first I was going to do a Windows 7 upgrade over Windows XP but didn't want to take the chance of losing my XP programs and files. Then I thought why not install Windows 7 on a separate drive and duel boot. Not understanding the OEM part I bought a Windows 7 DVD from Tiger Direct. Now that I have it, I noticed the OPK part and did some research on this site. I guess from what I found I can install it on my computer since I built it. Hmmmm! I was planning to set up the duel boot using EasyBCD. The copy of XP is on 2 HDDs with a RAID setup. I want to put Windows 7 on a SSD. Even though I'm putting an OEM Windows 7 on a separate drive will it see XP and complain? I haven't opened the package yet so if need be I'm hoping I could send it back and bite the bullet for the upgrade which I now see is over $250. But that brings up another question. Can I install an upgrade on the SSD and not the drives with XP and still duel boot? Or does the upgrade have to be installed over the top of XP?