|See the link below for a better explanation of what you may be calling OEM. Your license may actually be SLP, not OEM.|
If you buy a copy of Windows from a vendor along with some hardware, you most likely are buying a full, OEM version. The OEM version is supposed to stay with the original hardware but Microsoft doesn't enforce that.
See the link below and read teh FAQs.
SLP versions will usually not install on a different series of computer. Just yesterday I attempted to install an SLP version of WinXP for a Compaq. It wouldn't work, saying the disk was for a different model of Compaq computer.
You can use the SLP Operating system disk if you have a product key. The product key must match the same series of hardware. Will sometimes work across brands with the same type of hardware. In other words it is a crap shoot.
One thing to note is the OEM key on the case is NOT the same as the key in the registry. The registry key will be the standard 5 groups of 5 number. The OEM may be . Recover the internal key from the hard drive. If the old system doesn't run anymore, I think the newer versions of magical jelly bean key finder will look at a slaved drive.