Personally I think it has to do with the drives themselves. When my Seagate drives were starting to die my POST times were about twice as long as they had been and the boot to windows logo from POST and subsequently from logo to login screen were all longer.
After replacing the drives all the times were reduced.
Phenom II 940 Black Edition quad core @ 3.5Ghz
2x1 gig OCZ PC26400 Platinum, 2x1gig GSkill PC26400
Upcoming EVGA GTX470
Some other stuff,
Even more stuff,
If the automobile had followed the same development cycle as the computer, a Rolls-Royce would today cost $100, get a million miles per gallon, and explode once a year, killing everyone inside. --Robert X. Cringely, InfoWorld magazine