By reinstalling windows, how does microsoft know two computers aren't using the same key?

My computer is really slow, so i'm wiping the drive and reinstalling. Will microsoft think that two different computers are using the same key and think i've pirated it?

By reinstalling windows, how does microsoft know two computers aren't using the same key?noton

No. As part of the install process, the Windows program takes information from your computer's components (hard drive, CPU, motherboard, etc.) and, along with that 25 digit Product Key, creates a unique one of a kind Product Identification number (PID). Each time you use that install disk (and each time you start your computer) an internal check is done to recreate the PID. If the PID matches the one stored in memory, eveyone is happy in Microsoft land. You can see the PID for your computer by clicking on Start, then right clicking on My Computer, then clicking Properties. You'll see a long number on the General tab just below the "registered to" info.

You can even change things about your computer (like memory, adding devices, etc.) and it won't affect the PID. But change something major, like the motherboard, and you might not get a match any more to the orginal PID. In which case you'd have to notify Microsoft tech support so they can help you "validate" your system. The tech support number is: 1-866-234-6020 (just in case.)