computer shuts off,,,,,,,house electric problem ?

my cpu shuts down before it logs onto xp, to make a very long story short an electrician said theres no problem with my electrical system (wires in house , plugs , breaker box) .
I had a friends cpu at my house plugged into same outlet with same outcome. When I plug into a different plug on other side of room cpu works fine. I have an apc battery backup that I bought the first time this happend I thought that fixed problem but here I am 7 months later with same issue. I cant move cpu to other side of room because of space issues and i cant leave a bright orange extension cord across the floor with my two young children . anyone ever had a problem like this before? suggestions or something I might be missing here? please help

Get a better electrician.

I mean if one outlet affects two computers in the same way: whereas they have no problems using other outlets...

Change the outlet. Make sure the poles aren't switched. Hot/Neutral visa/versa. Also if the outlet happens to be a Ground Fault Interrupt then replace it with a standard outlet.