I used to work for a large power company that used exclusively Compaqs. All of their computers got into the BIOS with the F10 key.
On most of them, when starting up, a little white box would blink on and off in the upper right corner of the screen. That was the cue to press the F10 key to enter the bios.
By the way, it looks like you have a Deskpro 4000 and on the Compaq website, it confirms that F10 enters the BIOS on this computer
Here is the Deskpro 4000 FAQ:
And some other links that might help:
[This message has been edited by Meatballman (edited 03-13-2001).]