Some PC's are slow booting and some are fast.
Depends on your hardware as well. If it's doing alot of stuff to hard ware, trying to boot off of different things, it gets slow.
Your BIOS, theirs settings that enable certain checks upon booting
Antivirus checks upon booting, yeah this does wonders to some PC's :P
How many services are you running? this affects your boot speed going into windows
And spyware, virus's and the age of the windows instalation also affect boot speed
My computers never boot fast. My laptop which is half the speed of my desktop, boots up in half the time my desktop does :/