Check my profile....

I haven't run any tests to model the situation you're asking about, but I suspect you have more reason to worry about the vibration upsetting your computer than the effects of magnetic interference from the speakers. A large transformer might be a problem, though, so I would avoid parking a laptop on large tube amps, just in case.

And a Windows system will crash at the most inconvenient times, even without outside provocation, yes? ;)