OS X :: Macbook Shuts Down Suddenly

This started about 2 days ago, there was no apparent signs of such a thing going to happen.

My MacBook suddenly shuts down in the middle of my work. Shut down as in a sudden shut down, as if the battery was removed. There is no shutdown process, the whole screen just goes black. I've realized that this happens more recently when watching youtube videos, playing flash games etc.

Example : Computer dies in 10 minutes when watching videos/playing games. Computer dies in a few hours or NEVER when just typing, surfing.

It doesn't seem to be a battery problem. I've removed the battery and had my Macbook run on the Charger before, and it still died on me...

Battery Information:

Battery Installed:Yes
First low level warning:No
Full Charge Capacity (mAh):4390
Remaining Capacity (mAh):2128
Amperage (mA):-1720
Voltage (mV):11081
Cycle Count:495

Mac OSX 10.4.11

1.83 GHz Intel Core 2 Duo
1.25GB 667 MHz DDR2 SDRAM
I run bootcamp, same problem on my other operating system

Hardware Overview:

Model Name:MacBook
Model Identifier:MacBook2,1
Processor Name:Intel Core 2 Duo
Processor Speed:1.83 GHz
Number Of Processors:1
Total Number Of Cores:2
L2 Cache (per processor):2 MB
Memory:1.25 GB
Bus Speed:667 MHz
Boot ROM Version:MB21.00A5.B07
SMC Version:1.13f3
Serial Number:4H7110U8WGK
Sudden Motion Sensor:
State:Enabled