If you'd asked that question last week the answer would probably have been no, but Microsoft have changed the licensing rules so you can now do this. But as anskyber has pointed out it would have to be the full version. OEM versions which are installed on a PC will I presume be the same as XP is now, that is it dies with the PC as is not transferable.
What I mean is; if you buy the OEM with say a hard-drive and when you rebuild your computer you retaine the hard-drive that you brought does this die? after all the OEM copy is linked to the hard drive?
I wonder if you buy a floopy drive, and has long as you are putting in the floopy drive to any computer you are building would this still count and stop the OEM licence dieing?