OEM cd's are "open ended" for PC manufacturers to change some components to tailor to their computer systems. (i.e Start pages, Logos, desktop icons, etc etc)
It doesnt allow them to change the core components of the OS.
You CAN install an OEM copy of an OS on ANY pc except those (DELL) that look for a specifice piece to run the install.
I have stacks and stacks of Windows 2000 Professional CD's from the 500-600 DELL pc's we bought, we dont have to return the cd's but they dont do much good with out a Dell Bios as was stated earlier.