Try closing applications in the background. If that does not work, try download Virtual Box and install Vista. Then try ajusting the memory to 512 MB. I do not use Boot Camp, but see if you can ajust the memory. That usually helps.
When running games on my bootcamp vista (MBP) the thing gets super hot. I know the trick of booting into Leopard and starting up smc fan control then restarting, but i would much rather use a more native solution if one exists....

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