回复：MS allows up to 8 (some said 11) activations for one product

In fact,if you reinstall your xp on the same---100% same hard ware,you also need activate the system,but if you have oem version,you only can activate one time,coz oem version is not for resall or sell.if you still want re-activata oem xp,you have only option to call microsoft and tell them your motherboard was dead,and you got exactly the same motherboard replacement.oem xp will detected and grab motherboard information during installation.
good luck.