I honestly do not know :( We have about 6 of them from a computer shop. To my understanding you can install windows or repair with this disk. All have been opened but you can barely even tell it as they were slid out and back in. Sorry I can't give a better answer there :(
You can usually install it on 3 pc and use the automatic activation. If you install it on 4 and up you sometimes have to use the phone activation. Xp is not on the top of there list now so they may have removed all the restrictions.