Studio monitor chaos

Hi
i just bought some krk v4 studio monitors and i can hear major computer noise coming out of them. man, i have tried everything to fix it i will list.
tried balanced and unbalanced leads, xlr's with ground lift connections, new planet waves gold plated usb cord, tried taking out my usb mouse, tried different powerpoints in the house for computer and speakers. yesterday i took the whole setup to a music shop and tried a different interface and it stopped it, so i thought fine, must be a dodgey interface. Also while i was there i tried the speakers running out of the phones jack on the computer with a splitter lead. it was fine.
So i get home, buy a new splitter lead and just run it out of the computer and bang there it is again. mouse noise, computer noises, everything!
The last thing i will mention is that when i run the laptop on battery and not the powerpack it stops, but every now and then i can here interference.
It appears to me the problem is in the computer or powerpack but i tell you its driving me nuts trying to figure it out. i really dont have a clue whats going on.
the laptop i have is brand new acer aspire 5760 and the speakers i was previously using were not making the noise although when i cranked it right up full i can hear the exact same stuff going on, just no where near as loud. these speakers were not powered just running out of the phones jack into an amp.
the last resort i can think of is have the computer powerpack checked and the computer checked.
I was really hoping you would know exactly what it is cause im at a loss.
Hope you can help
Deon