I've done some searching, both g00gle and here in the forum, but found no suitable answers. What I wanted to find out is info about the particular group elements of the product id numbers. For instance with XP if the first 5 digits were 55277 it was an XP Home, if they were 55274 it was XP Pro. If the numbers were 76487 it was XP Pro, if 76477 it was XP Home - both of these were from keys after SP1a. Depending on the key used; the next group of 3 could be OEM - self explanatory, 640 - 649 was a corporate key, 020 was for an upgrade professional key, and I don't know what the retail key was, 'cause I never bought one! In a similar vein, with Vista UltimateRetail Key gave a code = 89587-447-XXXXXXX-XXXXX. I know from personal info that the following is true; Windows 7 Home Premium Retail Key is = 00359-112-XXXXXXX-XXXXX Windows 7 Business Upgrade Key is = 00371-840-XXXXXXX-XXXXX Windows 7 Ultimate Signature Edition Key is = 00426-292-XXXXXXX-XXXXX Windows 7 Any Time Upgrade to Ultimate Key is = 00426-104-XXXXXXX-XXXXX So if I have a Windows 7 Ultimate key and the I.D. is 00426-437-XXXXXXX-XXXXX then what type of key is it? Would be great if some sort of reference chart could be generated, using info supplied by other members. For instance what kind of Product I.D. numbers do MSDN and Technet keys generate?