XP Game Crashes

I built my computer in November with these specs:

-Antec SOHO Server Case (4 5" drive bays, 6 3.5" drive bays, 4 fans [2 front, 2 back], 400W Power Supply)
-Pentium 4 2.66 Ghz processor (NOT OVERCLOCKED YET [past 3 Ghz], heatsink and fan included)
-MSI Neo2 865PE Motherboard (10 USB ports, Mouse, Keyboard, etc.)
-512 MB PNY DDR SDRAM
-ATI Radeon 9600 128 MB Gfx AGP Card
-Maxtor 80GB 7200 RPM HDD
-Liteon CD-R/CD-RW/DVD-R/DVD+-RW/DVD--RW Drive
-Generic DVD-ROM drive (can't remember the brand name)
-10 year old 3.5" Floppy Drive that doesn't work
-Windows XP Home

Sorry for all of the useless info, its just a copy/paste job from my own forums. (WHICH YOU SHOULD JOIN!)

I am having trouble with a few games, namely being MechWarrior 3, Zoombinis Mountain Rescue, Croc2, and LEGO Racer 2. When I start them, and I click EVEN ONCE, they crash out to the desktop with no warnings or anything. Its just a quick flash from whatever screen I was on, to a black screen, and then to the desktop. I'm not sure what's causing this and that's why I'm here. Hopefully you guys can help, because I'm clueless...

[Jason425]

latest drivers and everything? Try running everything at the stock speed. Get the latest patches.. mess around with the drivers for the video card

[Prometheus]

resolution of games?

new monitor?

I just updated the ATI Radeon 9600 drivers, I updated the MSI Motherboard drivers, and I checked all of the games that I am having trouble with for updates and I have installed everything. The thing is, it still won't work.

I'm not a techie like you guys, so I don't know what "stock speed" is. And my monitor is a 19" ProView monitor that I got off of newegg.com in November. The resolution of the games varies. I think MW3 is 640x480, Zoombinis is 800x600, Croc2 is 800x600, and LEGO Racer 2 is 800x600 - but I can't be sure of all of those because they obviously won't work for me. Also, when I get to certain points of certain levels in Lemmings Revolution (800x600) it crashes to a black screen and then the desktop as well. This is getting REALLY ANNOYING! *bangs head off of wall* Back to trying to fiddle with stuff...

[Prometheus]

try system restore to a time when the games DID work

That's the point, they never HAVE worked. Or else that's what I would've done...

[Prometheus]

try running them in compatibility mode for win 98

Once again with the stupidity: HOW DO I DO THAT?

[Prometheus]

right click on the shortcut for the game

look around youll find it

Ok, well the Zoombinis Mountain Rescue works, but the sound is horrific! Is there any way to fix that?