Hey im trying to reinstall my OS on my laptop i obtained a disk form a friend and used my own licence key located under the laptop but it tells me it is not a valid key , Does it make a difference if the disk is a OEM or Retail disk if so how do i know what i have? Thanks

It does make a difference. If the laptop came with the OS installed you need a disk of the same type, i.e. an OEM disk the laptop manufacture. It know because of the key you enter with will only work with an OEM disk. Depending on the manufacturer you should be able to get a recovery disk from them for a small fee. Stuart

Thanks I have done some further checking and as far as I can tell a RTM version of the OS will work for all legitimate keys, I have not tested this but thought I would let you know.