New Ati 2400 Drivers - ?

Hello everyone. Just to let you know, I'm new here, and have little to no technical knowledge regarding hardware- or software-related problems. So here's my dilemma -

I recently received a new Gateway GT5662 off of Newegg.com, and the specs are as follows:
3GB RAM
500GB Hard Drive
AMD Phenom 9500
ATI 2400XT
Windows Vista Home Premium (32-bit)
Hanns-G 19" LCD Monitor

This computer was great out of the box and still runs perfectly, with the exception of when I decide to run Counter-Strike or Half-Life 2, where it will run for about 2-3 minutes before the screen flickers, blackens, and the game quits back to the desktop, with an "Engine Error" message popping up, reading: "failed to lock vertex buffer in CMeshDX8::LockVertexBuffer

I figured this could be due to faulty graphics drivers on the 2400XT or, perhaps ATI Catalyst Control Center. So, I went to the ATI website and tried downloading the latest driver for both with the URL as follows - http://game.amd.com/us-en/drivers_ [...] on-vista32
But when trying to run either one, programs labeled "8-1_vista32_dd_57724.exe" and "8-1_vista32-64_ccc_lang1_57726.exe" respectively, it started running a CMD Window, and game me the following error message in a window labeled "16 bit MS-DOS Subsystem":
"C:\Users\Dylan\Desktop\8-1_VI~3.exe
The NTVDM CPU has encountered an illegal instruction.
CS:11d9 IP:0273 OP:63 75 6d 65 6e Choose 'Close' to terminate the application."

The driver I have for my 2400XT is version "8.403.0.0", and for Catalyst Control Center it's "Catalyst® Control Center Version 2007.0815.2326.40058"

Any advice and/or insight into this issue would be greatly appreciated.

Thanks,
Dylan

p.s. today it started artifacting and several times, the monitor rebooted and i get a warning sign display saying that my graphics card basically crashed and just recovered..somebody please help!! this is a bradn new computer and i am growing very anxious to start using it!!! could it possibly have anything to do with my monitor? i have a VGA cord running from the vga input on the monitor (blue plug) to whatever input is on the back of my graphics card (a larger white plug)