What it does (also called System Builder) with an OEM version all about? It is exactly the same product as in the more expensive "retail" version. The only restrictions: There is no phone support and Microsoft this version you must always run on a single PC - not on several simultaneously. Should you buy a new PC after some time, you can install this version without any problems on this. You should then delete the Windows but your old PC because there are problems with the "activation" of Windows on the new PC otherwise.
For hotline: I have now since 1997 to deal with PCs and had the services of Microsoft never avail. In Windows problems are the many computer forums on the Internet or the computer expert from the circle anyway better, cheaper and more personal choice.
I recommend everyone to buy this OEM / System Builder version because you thereby saving a lot of money and this is still dealing with the 100% full version.