How do I tell if it's a pirated copy or not?

I have this HP computer in question, the owners took it in to a computer tech repair guy. He replaced the motherboard, and then installed XP Pro on the system. It originally came with Home edition. The customer did not request for XP Pro to be installed. They were not charge for XP Pro, just the replaced mobo and time, and they (the customer) didn't receive a copy of the OS that was installed.

My question is, is this a legit copy, if so how do I know. I have the product key that was used, do I have to call MS to verify this key? I feel the customer should have gotten a disc, since the key can't be reused on a different PC.

This site was designed to answer that question.

"HowTo Tell?"

http://www.microsoft.com/piracy/htt/

Here's Microsoft's Software Inventory Analyzer. Download it and it will check your software.

http://www.microsoft.com/resources/sam/msia/default.asp

Thanks, I believe the first link should do. I'd be a while before I'm able to verify this. Thanks again.

Microsoft has an 800 number that you can call and they will be able to verify if it is legit or not.