I have a problem with my emachine?

I have something that keeps happening to my laptop. I will start it up and it will go to a blue screen. On the screen it will tell me how it has been stopped by windows in order to protect it. I am not sure if it gives the same code each time but this time the code was

stop 0x00000050 (0xDD5893A4,0x00000000,0x804E70D5,0x00000000)

I dont know what to do about it. I turn it off and wait to restart it. I will also shut down by itself for no reason anytime. This causes big problems because I work from my computer and this will happen right in the middle of my work.

eMachines
M5312
Mobile AMD Athlon XP 2400+
1.79 GHz, 448 MB
Windows XP 2002
Service Pack 2

Jennifer
July 2007