I have no idea on how to work with GRUB in this situation, but why not use BCD (Windows Boot Loader)?? It's much easier to use, and there's very few command-line commands needed to install and/or keep up with what's installed.
This works for Vista Home premium (All Vista versions except for Starter) and Windows 7 (minus starter).
Boot using the Windows rescue disc, or the installation media. Either way, it doesn't matter. Go to the options that include a command prompt, and a few other of the rescue tools. At the prompt, type 'Bootrec.exe /FixMbr', and enter. Reboot, and you have the ability to boot Windows. This option requires setup from within the Windows system, therefore you shouldn't see Linux (and any other OS's you have) on the listing right away. Boot into Windows, install 'EasyBCD', and add an entry for any other OS you have. All done :-)
EasyBCD is a million times easier than working with GRUB, and it's much more convenient to use. Plus, if you have Windows installed, why not use it anyway?? It's absolutely no faster, or slower, than Linux.