Video card and monitor are killing themselves

I have a Geforce fx5200 256 meg graphics card, OS is XP professional,
512 ram, MBO is ASUS a7v600-x, and monitor samsung syncmaster 793 df.

I can play a game like Sims2 without any problem whatsoever, but when I
play another particular game (Battlefield 1942; Avp2; Toca Race Driver)
the game will almost without fail - at differing intervals - cause my
monitor to go into Standby Mode, from which there is no escape bar a
reboot of the system. Sometimes my monitor displays message " Hz ? " or
something similar ("sync out of range" maybe) and sometimes it doesn't,
but just goes to standby, or sometimes it reboots automaticaly.

There is a facility within the game to allow you to check that your
graphics card has the correct drivers etc and that I have the correct
DirectX installed and when I use this the game says I have everything
correctly installed and that I am ready for play.....but I am not, I
constantly get kicked into Standby mode.

It can't be a heat issue as I can run other games for hours and have no
problem....also, I can turn the computer on for the first time in the
day, run the Avp2 game and get kicked into Standby mode within two
minutes of the computer starting which hardly indicates a temperature issue.

I have updated the audio drivers and I have also fiddled with the
monitor refresh rate. I have reinstalled the game a number of times.
I've replaced a thermal paste on card so there can't be any of
overheating problems.

When I get kicked into Standby mode I can hear (about 50% of the time
anyway) the game TRYING to run; ie: I have a totally black screen but I
can hear the sound of the game running, but with the broken record
effect...ie: one bit of sound looping over and over, as if the game is
stuck.

There have been occasions when I have run the game for an hour without
any problem whatsoever and then other times as soon as I load a saved
game it kicks the monitor straight into Standby mode.....which is
beginning to make me think about kicking the monitor straight out the
window.

I have the latest DirectX installed and my computer more than meets
specified minimum requirements to run the game.

I did some cursory investigation into monitor refresh rates..... My
refresh rate is 85...I changed it to 75 and then 60 and the same thing
happens.

Can the monitor refresh rate be different for different games?

Can anyone please help?
I AM GOING INSANE!!!!!!

nope. none of that problems. My card isnt overheating and no supply
probs. What could be wrong between direct x and my gfx card (with agp 8x
ability)? i've installed dx9c today and noticed some changes but the
problem isnt solved. For example my mouse pointer was leaving
undeleteable trail on menu screen in Rome: total war and now it doesnt
but now comp freezes after 5 seconds in game. So there were some changes
when i installed new dx but what can I do to diagnose the problem with
dx and gfxcard?