Microsoft are not hanging around, with their offer on win 8 out already.
http://windows.microsoft.com/en-US/w.../upgrade-offer
http://windows.microsoft.com/en-US/w.../upgrade-offer
However, the Vista is tied to the dead motherboard, so here I am essentially without an OS. If I buy Windows 7 now, I am not buying another OS in October or even next year. The TOS of the Windows 8 customer preview says I may not use it as my main operating system. Given what I have seen of Windows 8 so far (and I only installed it yesterday), I'd rather wait, as the repairman suggested.
Stand to be corrected here as things may have changed but I had a motherboard go down which was linked to an OEM OS. Fitted a replacement motherboard as the original vendor had gone AWOL so the guarantee was as useful as an ashtray on a motorbike. Come licensing time and MS re-validated without any problems whatsoever.