First start by putting your hand behind the power supply fan out let (its the big outlet at the back with usually circular grids. You should feel a small draft and maybe here the fan.
If the above is OK then turnSounds as though one of your fans has packed it in -
TURN THE COMPUTER OFF AND PULL THE POWER PLUG OUT - then open the case. Stand back and turn the power and computer on DONT TOUCH ANYTHING - see if the fan over the CPU is operating.
Alternatively your computer may have come with heat sensors which can be read from the bios setup - look in your computer manual to see if you have that option - sometimes its not in the bios but if your CPU has heat sensors you should have received a program that monitors your CPU temp and fan speed.
I thought I would come here and see if anyone has any expertise before I go and buy another computer. Here is the problem. About a month ago my computer made some odd sound then about 2 minutes later it shut down. I push the start button and it runs for 5-10 seconds and it shuts down again. I keep doing that 5 times or so and finally it runs. Yesterday again it shuts down while I am sitting here. Again it takes several times of me trying to start it before it stays up and running. I have tried to run some spybot program and a virus scan but when I do it runs for awhile and then shuts down. If I am just looking on the net it is fine. I have also noticed that my modem is running slower. I was running about 50kbps a few weeks ago and now it is down to 29. The computer has been slower to load but I think that is due to the slower modem speed. I have a Dell Deminsion 2350 that is just over 2 years old. It has been used quite a bit so maybe I have just worn it out. Anyone have any suggestions?