I was advised to go the extra and get the Professional version. There was not that much difference in the price of OEM versions. There is an upgrade version as well which is cheaper over here. Apparently it is a full version unlike past upgrades, all you require to install it is a valid versions of a previous version of windows (don’t know how far back it goes) to install it. From what I have been told it dose not over install over the current Windows like it used to do, it performs a clean install.