Hm, I am a little confused.

You have two monitors

One produces this "control lock" and the other does not?

One does not show anything until you get to the desktop...........what about the other?

'Unlocked'... i can press the button to my menu[where you adjust yur screen, contrast, brightness, etc] but when it pops to 'Locked'.. i wont be able to access the menu. y'know what i mean?
That bit I understand, the "lock" is to prevent the user from changing system settings, as farv as I know.

Do you get the same results if you log on as administrator?

Also, take a look in your BIOS/CMOS settings and see if "Fast Boot" is enabled, and if there is an option to disable control lock.

What are the makes and models of your monitors? Do they have built in speakers, or do you have stand alone speakers. Try switching them off and see if you still get the "clicks"

I have seen some strange things with Win XP when you don't have the right driver for a monitor. If you look in Control Panel, Display, and Settings it should tell you the monitor and video card that your system thinks that it is running with............is it correct?

Do you get the problem when you boot into Safe Mode?

EDIT:

I didn't ask, but is there any third party parental/access control software running?

Also, does your monitor settings have a settings locking option?