unable to startx on Compaq

[Liudmila Yafremava <liudmila@spine.npa.uiuc.edu>]

Hello!

I installed debian on Compaq Presario 1200T (12XL3). My problem is
that startx does not connect to terminal. I am unsure what driver to
use for my videocard, so I used vesa. Monitor resolution 800x600@16.
Videocard memory unknown: compaq does not provide that information. 
When I reconfigure the mouse and test it with  
XFree86 -xf86config /root/XF86Config.new
I see a purely black screen, and sometimes gray screen, no X for mouse,
and when I try to exit, ctrl-alt-bckspc does not work. 

I guess, my problem is video adapter configuration, but I have no idea
what to do. Each time after  ctrl-alt-bckspc fails, I have to do a hard
reboot, and that breaks something in the kernel, so the computer suggests
me to do a manual repair, but I do not know how.

I am a newbie - please spoonfeed, or point to helpful websites with info
on videocard/mouse/Xfree configuration.

Thank you much,
Luda