To overcome all kind of problems I have a machine with a second XP installation on a second hard drive. I disabled several hardware items in that GS3 profile to make it as efficient as possible. When windows wanted to install drivers for hardware that I don´t need I stopped the wizard and answered no to the question if windows must ask again to install drivers for that hardware device.

This way I created two different XP installations on one machine: One for GS3 editing and sequencing with Cubase and another one for GS2 editing and sequencing with Logic and all my VSTi´s.
I now have GS2 and GS3 on the same machine!

Switching between profiles is as easy as rebooting and selecting the proper OS from the win startup menu.
Have fun!