Laptop causes hissing through mixer

[tonedef]

When I turn on my laptop, it causes hissing to my mixer and through my monitors. even when the inputs to my mbox aren't connected to the mixer. This is kinda weird because it hisses when the laptop isn't even connected to the mixer. Am I getting some type of interference?

[bb_aus]

its likley a grounding issue due to the way most laptop power supplies are made.
simple thing to check is does it do it when you run the laptop from the battery
if not then lift the groud pin on your cables connecting to the mixer.