PCs running Windows XP or Windows Vista take a long time to boot up. This is especially true if you use a Mac which seems to be responsive soon after its boots. I've used a variety of Windows PCs over the years. And, everything including the Dell Latitude D620 with a Core 2 Duo processor took many minutes from booting to being usable. In fact, the much older and less powerful Dell Dimension 2400 with a Celeron processor booted much faster and was usable much sooner than the Dell notebook. This was because the Dimension ran Windows XP while the D620 ran Windows Vista. And, the Dimension had a faster 7200rpm hard drive while the notebook had, if I recall correctly, a 5400rpm drive.
A third factor that messes up boot times are the various security and call-home-for-update processes that all fire at start-time. If you look at the processes running soon after boot (as soon as Ctrl-Alt-Del can actually work since it is stymied by the slow boot process too), you will see all kinds of junk apps calling home for updates while various security apps perform their tasks too.
This all leads to what for me is up to a 5 minute wait until my various Windows PCs are responsive and ready for actual work.