Thanks Bass. I think the time interval thing makes sense rather than the number of times you do it. Just having an issue right now with my windows 7 installation and I had to do it twice and activate it twice within 24hrs as the first installation was very unstable and I don't know why. But both got activated successfully. I am getting a lot of program stoppage notifications. Could be the chipset driver. Not sure.
Microsoft licenses are, to say the least, somewhat dubious. I would imagine OEM are timeless, limited only by the lifespan of the OS. The thing is, if you install Windows on a "new computer", which practically means a new mobo - new memories are of no concern, neither a new CPU or GPU, or these combined.
In full versions, like I have 7 Pro, they give 20 downloads. Then again, having stopped the sell of Win 7, what does it mean?