Windows crashes when I am not working on it

[Breezer]

I get blue screen and my computer boots

error message:

BCCode : f4 BCP1 : 00000003 BCP2 : 8868D6E8 BCP3 : 8868D85C BCP4 : 805C7478

When I am not working with my computer, crashes about half hour after it and what makes this strange it wont crash while I work with it.

Any idea what causes this?

sorry my bad english...

2.21 GHz, AMD Athlon 64 Processor 3500+
nVidia GeForce 7800 GTX
Windows XP Professional, Service Pack 2

 

[fastco]

GO here and follow the instructions then zip up a few minidumps so we can check them. https://www.techspot.com/vb/topic51365.html