In the forum postings I've seen here most people building new computers buy the OEM version of Windows. If the OEM version can be installed on only on model motherboard it seems to me that one is assuming that the OS (and it's upgrade license) will be obsolete before the cpu. Usually if one upgrades the cpu a few years down the road the MB will need to be replaced.
Should I buy the full versions of Windows 7 so I don't have to buy it again when I upgrade my computer, or am I missing something?
I suspect that MS would be more sympathetic to an upgrade due to failure than due to obsolescence.
Either way it really bothers me to have to ask Uncle Bill for permission every time I get under the hood.
I guess my only alternatives are to switch to Linux or throw in the towel and buy a Mac (give up building my own.)
Don't buy a Mac. If you think that Bill is restrictive you should see some of the doozies that Steve manages to come up with. I'm firmly convinced that the days of Apple computers (as opposed to their consumer stuff) are numbered; people just won't put up with the restrictions that Apple want to place on what you can do with the hardware, what programs you can load on it.
Stick with the Linux idea - if you don't like it you get a full refund on the purchase price.