blank screen as part of start-up?

I installed Windows 7 Professional without problems, including updating all my drivers.
After loading the basic operating system I noticed, as part of the boot-up process, following the 4 colour moving Microsoft logo, there then follows exactly 60 seconds of blank screen, followed by the final few seconds of the boot up process involving the Welcome screen etc. The machine then works fine in all respects.
This 60 seconds of blank screen may be a normal part of the boot-up process, but what I don't understand is that, having loaded an increasing number of software applications (e.g. Office etc.) this 60 seconds never gets longer or shorter. Clearly during this time the OS and applications are loading (although there is only a little HDD activity indicated by my red light), so why is this time always 60 seconds: or is this part of the normal boot-up process?
I clearly don't have a problem but I am just VERY curious.

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