Do not use OEM version of Windows?

They probably say that because the OEM is usually tied to a machine and it's a license that may have been already activated. And most OEM copies are DELL which won't install on non-DELL machines (at least never for me).

 

The only problems I can think using an OEM license would present is it's much more likely the activation key would already have been used, since manufacturers often use the same keys several times. Microsoft is normally okay with this though, you just have to go through the trouble of calling them to activate it rather than just doing it over the Web as with a retail copy.

 

Yes, you'll be perfectly fine. I've used an OEM version myself in the past and had no problems whatsoever.

 

Yes.