Using Vista on two machines..?

Hey,

I have a genuine retail version of Windows Vista Home Premium which I currently use on my PC.

I'm getting a MacBook at Christmas and I'd like to run it on there too. I'm aware that this breaks the EULA, but how likely is it that Microsoft will actually notice and break Windows on one (or both) of my machines?

So far it's only ever been installed on this PC, so I'd like to think they'd target the people who are pirating millions of copies of Vista rather than the people who spend £200 and just want to get their money's worth.

It is Microsoft though, so I thought I'd better check ...

Thanks.