My Computer shuts off and makes a siren noise when i play a windows based MMO?

Question

I play an Online game called dark age of camelot. Up until recently there was never any problems. Now, everytime i play within 5-30 mins my computer shuts off and makes an alarm or siren type of noise until i turn off the power strip. But it only does this when i play the game and never had any problems until recently. Here is my Computer Stats are

AMD Athlon(tm) XP 2800+
NVIDIA GeForce FX 5200 128 MB
74 gig HD, with 20 Gigs free
1024 megs of ram
Direct X 9c with Windows XP
3 meg cable internet

I cant think of any software I installed around that time that it started doing this. It really is an annoying noise that in my opinion sounds like something serious, but it NEVER does otherwise. Also it is a bit laggy as startup which is new. Ive used Adaware,Windows Defender and HiJackthis as i am somewhat computer savvy. Also Windows Live One Care, all show a clean log. Uninstalled nearly all other software that wasent required. Completely stumped. Can anyone please help?

The name is from a previously asked question - Here is the game requirements

PII 450
256mb RAM
600mb free hard drive space
32mb 3D accelerated video card

Sorry those were an earlier versions spce, Current specs are

Pentium 4 2.0 GHz or AMD equivalent
512 MB RAM
Requires compatible 3D acceleration card with 64 MB Video RAM (with Pixel Shader 1.1 or higher)
DirectX 9.0c or later

Been playing for 4 months on this setup with no problems at all, smooth playing

That could be as the computer takes up some memory, I thought I have seen software that will check the internal temp, does that require a thermometer though(one would think) but otherwise never any problems except in game

Cleaned startup, registry, and jus removed a few programs that werent required..pretty simple setup as far as installed prgrams

Answer 1

Your CPU overheating and shutting itself off to save your itself from frying?

If your pc is lagging check start, run, msconfig, startup list. free up some of the checked programs starting with xp

Answer 2

how big is your power supply, cause with todays games you need at least 450 watt power also check to see if the video card needs to plug up to the power supply. also maybe need more ram always want/need at lest 2 gigs. sounds like a performance problem. does lag or does the game lag at startup? because that can be indicative of 2 different problems. my cousin and husband are interested in your problem hit me up through im or e-mail and they will gladly help you work through the problem both have gone to school for electronics