System rebuild and Windows activation

[stevenrw]

I'd just like some clarification on Windows activation chaps.
I understand that changing your hard drive, memory and motherboard constitutes a new machine in MS' eyes and as such your existing OEM version of W7 may not be activated.
Annoying, but understandable (sort of)
But conversely if you move your existing motherboard complete with its memory and the same hard drive to another case with different sound/graphics cards, would it just boot up as normal? No need to reinstall or reactivate.
I'm putting a new bundle in with a bigger SSD and I'm going to use the old hardware in another case as a spare machine. Might upgrade that to W10 to see whats what before going over on the main machine.

[Technical Ben]

Is it a store purchased system or a windows 7 install from a disk?

If it's Windows from a disk, you can retype the key from the side of the PC or from the DVD box.

If it's a purchased PC with an OEM (as you say above), then you can get some assistance from MS, but may need to call. If it's an upgrade/replacement, just mention "I have put a new bigger HDD" or "my motherboard exploded" etc, the worse that can happen is they say no. But in my experience they always said yes.

You could sweeten the deal by letting them know you "are thinking of trying 10 after installing 7".     

If your changing more than one bit of hardware though, it may be harder. In all honesty, they could see "oh, 1 pc 1 license", but that would be too much like work for them.