The main issue seems to be with AMD processors when the manufacturer used an unified image for both Intel and AMD processors. I believe the installation does not realize that the processor specific work arounds are all in one file and just puts the Intel workaround file in place. This causes AMD processors not to boot. Pretty much every processor has quirks that the operating system has to have special case handlers to work around.
Thats funny I read this today due to just this morning our Database guy came in and said he could not get SP3 loaded on his home machine. He has a AMD Processor and it seems to be the issue. His work laptop loaded SP3 fine but its Intel... Just another reason I always recommend Intel and Nivida due to less issues and drivers are better. AMD and ATI are good but they tend to always have more bugs but like mike123abc said they all have their quirks..