Computer Shuts Down while playing game

Is it any particular game? Has it always done it or have you added any program or hardware?

Also make sure your system meets your game requirements. Your 810MB has on chip video which may have it limitations.

How much memory do you have??

Type
MEM at your dos prompt and see what kind in memory you have to run games.

C:\>MEM/?
Displays the amount of used and free memory in your system.

MEM [/CLASSIFY | /DEBUG | /FREE | /MODULE modulename] [/PAGE]

/CLASSIFY or /C  Classifies programs by memory usage. Lists the size of
programs, provides a summary of memory in use, and lists
largest memory block available.

/DEBUG or /D     Displays status of all modules in memory, internal drivers,
and other information.

/FREE or /F      Displays information about the amount of free memory left
in both conventional and upper memory.

/MODULE or /M    Displays a detailed listing of a module's memory use.
This option must be followed by the name of a module,
optionally separated from /M by a colon.

/PAGE or /P      Pauses after each screenful of information.

Regards, Bud
http://www.geocities.com/budallen98_98/ 
Bud's Win95 Win98 Tips and Troubleshooter

Intel 810 Board - - may need to be replaced as there is a recall - there is a link to download software and then check it:

http://www.intel.com/support/mth/ami.htm

mine tested OK.

Okay this is going to sound really stupid, but check your video card temperature. I had a major problem earlier this year when my card went into 3d mode teh computer would shut itself down because the card would overheat really badly.

If it is the card a nice fat fan sitting over the card seems to have solved my problem

Have you tried turning off any power-related features or screensavers?

have you gone to game manufacture sight for posible patches on you system?
do you have  ALL of the system updates?
Have you check to see if you have the latest flash BIOS update?
Have you check different messages boards to see it there is a motherboard version conflict? ( I found for gigabyte 5ax ver4.1  many probs but with ver5.2 none)
Do you have a generic powersupply? (maybe pulling too much power)
Is your Vidio card HOT after  the system fails?
Is your CPU hot after the system fails?

sysopt.com  
 and for powersupplys     pcpowerandcooling.com

See if your CPU fan is working. If not get a new one ASAP. Try taking your computer's case off so it will be cooler inside.

Well it seems I've solved the problem

When I disabled ACPI in BIOS, the problem got solved and now I can play the games without any problem.

But still I'ld like to know the correct result. If some one can tell,

I'm going to try bombinmad's suggetion if that is the case I would like to give my points to him.