[gabri3l]

I have heard some people installing with a 642 and 648, Some keys fall in that range. But here is the basis of the keys. (I am using someone elses explanation) If you use pirated or legit xp pro vlks check your product ID and your xp product code will look something like this: 55274-64X-XXXXXXX-XXXXX. Look at the ID as this: AAAAA-BBB-CCCCCCC-DDEEE. A is the product code. BBB is a significant number to the private key. C is the least significant of the private key. DD is the private algorithm key used to verify the 25 digit key. EEE is a random digit that changes each install, this is how activation remains random. BBB-CCCCCCC is your hidden product id, which will be within the above stated range if you use a legit microsoft created key. So some xp keys in the 64x range work just out of random luck but if you do not own a legit XP, the safest bet is to look for MSkey4in1 and gen a new 640 key.

Edit: It seems that issued keys from MS are 640-0005xxx to 640-0006xxx so when using MSkey to gen a key choose Windows XP Pro VLK and set the range as 640-500 to 640-600.