XP shutdown Explorer.exe problem

Hello,

I have a Dell Inspiron 530 that belongs to a friend. It's running XP Pro
and has 3gb ram. Nearly every time you shutdown, reboot or log off, this
error pops up:

"Explorer.EXE-Application Error
The instruction at 0x01359430 referenced memory at 0x01359430. The memory
could not be written." (The memory address changes from one time to the next)

I have searched till I can't see straight and can't find the solution to
this. I've run chkdisk, defragged and also sfc but to no avail. I have
removed all unnecessary items from startup and services in msconfig, but the
problem still exists.

Any guidance on resolving this would be greatly appreciated.
.