If the ram passes a complete memory test once, it should pass it again no matter how many times you run it. If you do get memory errors after it passes once, or even if it doesn't pass once, the contacts on the ram modules may have a poor connection.
See response 2 in this - try cleaning the contacts on the ram modules.
http://www.computing.net/hardware/w...
Then run a memory test again - in most cases you will no longer get any memory errors.
If you have the proper ram that is compatible with your mboard, and you are not overclocking the mboard, you should have no problems with the ram, other that possibly the above, unless the ram has been damaged by something external to it such as a faulty PS that is or was producing too much voltage, or a bad power spike or surge that your computer and everything that connects to it was not protected from, or a short of anything connected to the mboard.
If your ram settings in the bios are set to Auto or to by SPD or similar, you do not need to mess with latency settings.
If those games are the only things you have problems with, there can be all sorts of reasons for a game to crash, especially if it is a demanding recent one. You could try checking the web sites of the game makers for mentions of the problems you are having and suggestions for your game, or the video makers web site for special purpose drivers, or either place for settings you need to turn off or on for certain games.
If your computer also crashes when you do other demanding things such as burn a DVD, there is a possibility you're got an inadequate or defective power supply.
Restarting randomly can be caused by software problems (usually it blue screens)or by a defective power supply (usually it black screens).
Failing power supplies are common and can cause your symptoms.
Check your PS.
See response 4 in this:
http://www.computing.net/hardware/w...
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Win XP is often set to reboot when it encounters an unrecoverable error.
Usually this occurs after a blue screen.
To have XP possibly display an error message instead of rebooting:
1. Click Start, and then right-click My Computer.
2. Click Properties.
3. Click the Advanced tab, and then click Settings under Startup and Recovery.
4. Under System failure, click to clear the Automatically restart check box.
5. Click OK, and then click OK.