From what i know a OEM version stays with a PC forever. But what if the PC breaks down and a new hard drive or motherboard is needed. Is it possible to reinstall the windows oem?
"If the motherboard is replaced because of a defect, the user does not need to acquire a new operating system license for the computer. The motherboard replacement must be the same make and model, or the same manufacturer’s replacement or equivalent, as defined by that manufacturer’s warranty."
I have never had MS deny a reactivation one time when told that the system had changed significant hardware. You will have to speak to a live person for this but they have always granted one additional activation from my experience.