How to determine what product a microsoft product key goes to?

Hi:

I recently bought secondhand a Microsoft action pack binder from 2005. And in that binder were not only disks that seemed out of place (e.g. a windows server 2003 R2 disk 1 and a virtual PC 2005 on the same disk sleeve) but also just some CD sleeves with product key is without a disk. My question is is there any tool, method, or site that I can use on my own to punch in the product key and identify what it goes to? That I can avoid having to call Microsoft at all. I dont mind having to do that, but it would be nicer if I could just do it on my own.

Please note that the product key labels in question look like the following:

PRODUCT key:
XXXXX-XXXXX-XXXXX-XXXXX-XXXXX

Thus, the label doesnt tell me what product it goes with.