Please HELP!@# problem with ProT LE on windows

I bought the Mbox2 from windows awhile ago and have an on again off again problem. I keep getting a ringing buzzing sound coming out of monitors as soon as I load Protools 7.0 up. When the monitors are on and the mbox is powered up, there is no odd sound coming out of my monitors. But as SOON AS I BRING up the protools 7.0 program, the sound comes out. Its a low buzzing, feedback kinda sound that is very aggrivating. I brought the mbox to a repair shop and it wouldn't even power up on 2 macs. I also have had a certified Prtools instuctor look at it and we can't figure it out. CAN SOMEONE PLEASE HELP ME BEFORE I HAVE TO PAY $3.00 A MIN???????????????? I bought this program months ago and can't even use it. I worked properly for a total of 1 1/2 months out of 1 yr of having it. I have even put 7.3.1 on it and its still the same problem. My computer is a HP Media Center

This is not a solution but Media Center is not recommended or supported for Protoools. It is knownto have unsolvable problems.

This problem has been found to have several possible causes: 1. Bad/nonexistent power ground. Check your outlets and make sure they have a proper ground. 2. Ground loops, usually caused by having gear plugged into two different circuits. You can try to connect all gear to one circuit to see if that helps. 3. Using balanced cables from the output of the Mbox 2 to your amp/speakers can also help. 4. Bad computer design - the computer is putting noise down the USB bus, which is being picked up by the Mbox 2. Some customers have reported success by using a Monster Ultimate Performance USB cable.

I have had a serious noise problem using my mbox2 with a compaq notebook while pluged in... the solution for me was to put a ground lift on the power supply for the computer, then everything was quiet. Having everything share the same ground did not work for me.