The retail version IIRC has a manual if you can call it one and tech support. You can do a clean install after your initial install and activation, but I don't think there is a limit. The OEM version gets attached to your mobo, so you can switch it out, but chances are by the time you switch mobo's you'll be getting a new rig with a new windows. Worse case you give microsoft a call. You can upgrade anything and perform reintallation. The full retail version and oem version have one license, so no installs on multiple systems. Unless you get their three license oem pack.