While I (nor anyone else here unless they actually work for the companies in question) can gaurantee the accuracy of this answer. If you have a warranty question, it's best that you call the manufacturer and speak with a manager (the people answering the phones usually have a script and can't (or are afraid) to deviate from it).
That said, companies will LIKELY deny you certain support if you are not using the OS the computer shipped with. They COULD (and some will) tell you to reinstall the OS that came with the system and then they will help you. Certain things that are obviously OS independent and/or can be tested using manufacturer supported utilities will likely be fine (running a manufacturer supported boot CD to test the Hard Drive, for example. Other things, like why the screen won't run above 640x480, may require the original OS.
As for virtualizing the OEM license, it is prohibited. Microsoft doesn't permit OEM licenses to be run in virtual environments.
If he uses a different OS/CD-Key on his laptop then wouldn't it be legal? I thought the only illegal part would be to use it in multiple computers. If he is going to format his computer than the VM would be the only instance of the OEM installation. – Juice – 2009-12-27T16:56:40.723
1the OEM installation has been activated with the original hardware, so installing windows with the same key it will fail the activation on a VM and you cannot legally use it. – None – 2009-12-27T16:59:06.087
Would getting a new CD-Key be the equivalent to purchasing a whole new licence? As Luminose mentioned, I would only be using the Windows OS as a single instance. – nitbuntu – 2009-12-27T17:00:43.913
yes, technically speaking, you will have to to purchase a new license if you want to use Windows in a virtual machine. there are different scenarios for various retail versions of Windows, but the rules on OEM licenses are very strict. – None – 2009-12-27T17:03:58.370
One more thing. Does the same hold true for Apple Macbooks and Mac OSX? – nitbuntu – 2009-12-27T17:05:13.907
Apple isn't really my domain, but from what i know, their licensing policy is even more restrictive than Microsoft's. – None – 2009-12-27T17:08:19.360