I want to purchase a brand new Toshiba or Lenovo laptop with the aim of formatting the hard drive, installing Ubuntu Linux OS and using the Windows OS as a Virtualbox virtual machine.
Would doing this invalidate the warranty that comes with these laptops?
Additionally, is it possible to legally use the Windows OS as a virtual machine, rather than on the HD?
no, installing a different operating system will not void the warranty. however, you may not be entitled to driver and software related technical support if you're using another OS.
and no, it would not be legal to use an OEM license with a virtual machine as it is technically speaking a different computer with different hardware (although virtualized).
I personally think it's a grey area. If the manufacturer doesn't support that specific version of the OS you're installing, they could very well deny honoring your support contract. I'm almost certain if you read the agreement, you'll find something of that nature. There has been evidence that an OS managing the hardware it's running on incorrectly can cause hardware failures.
I would suggest making a clone of the OS the laptop shipped with and storing it somewhere, so if you ever do have to send it in for hardware repairs, you can put it back to it's original state assuming the hard drive isn't the problem and you have another computer to do the clone.
As far as Apple hardware is concerned, I think if you show up at the Genius Bar dual-booting Ubuntu, you're going to get turned away.
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.
