Heheh, leave it to MS to word their agreement like that.
The one caveat is that the license is tied to the motherboard only in as much as the system builder may replace the motherboard with a different one due to failure of the one installed and the license is still valid. As a system builder, I have asked MS on their system builder forums about that very thing and was told that as long as I was the system builder there was no issue with installing a new motherboard due to me being the one that had to support the installation in the first place.
As a system builder there were times when getting the same motherboard during our warranty period was either impossible, or not cost effective. We would ultimately put in what ever the customer wanted even if they wanted to pay for an upgrade and had the old system for almost a year, so we were still within the technical description of the OEM license when doing our upgrades.
That being said, yes I have been out of system building for a living for a couple of years and had forgotten that little caveat.
@
adrian, Yes the HD 6950 is slightly older but does that mean the performance is any lower? No. The fact of the matter is that the performance without overclocking on the GT 640 is quite a bit lower than the 6950 in all but power consumption and noise areas. For a gaming rig, yes, plan for the future, but if you have a budget and are looking for the best bang for the buck, older tech as long as it is still valid performance wise is the way to go to save some cash.
I personally steer customers towards the newer graphics cards due to what you are talking about when there is no budget limit because the price difference isn't usually that huge. The price difference between an HD 6950 and the newer HD 7950 is $100.00 US, and is most likely due to the 7950 having 3Gb of DDR5 ram instead of 2Gb like the 6950.
Bottom line we all have our criteria that we need to follow when we are looking to build new or upgrade. Yes everyone has an opinion, but a good hardware tech will tell you straight up which is better without having to send you to an overclocking site to see what the max is. I seldom recommend any kind of overclocking due to the potential of damaging hardware in the process.