Some of the faster times listed are for gaming systems, restarts, or restarts from hibernation mode. MACs really do start up in 20 seconds or less, from a cold, power off startup. But I have a compaq presario running xp pro with a 1.79 Ghz AMD processor and 512MB of memory that boots up cold in under a minute too. Here's how I do it:
streamline the startup list:
get rid of unnecessary processes: factory-installed spyware, extra toolbars, system hooks, apps you don't use, windows messenger, and especially anything from yahoo or myspace
Use mozilla firefox instead of internet explorer
Download windows xp manager (or vista manager if applicable) and use it to clean up junk files, your system's registry (the registry defrag option alone will cut your startup time by 20%), and other tweaks that are available.
http://www.yamicsoft.com
run ccleaner
use the run function and type chkdsk.exe /r
you'll have to restart
defrag your HDD as many times consecutively as it takes to consolidate all your files into one or two large groups with no small gaps (large gaps are ok), usually 3-5 times in a row
I use ghost to restore my HDDs on my desktop system every week after I make a backup of downloads and other files. It starts up vista ultimate in 35 seconds, but ghost costs $70.