Default directories annoyance with Win7 multiboot

[olav]

Hi,
I have a multiboot PC and where I run UE from more than one OS.
When I boot Win7 the disk mappings are altered because Win7 insiste that that partition should be named C:, and this moves the other drives one step down the alphabet. As the default Save Directories are stored in a file, this messes up the save paths, because when I boot Win7 my G drive is at H.
Is it possible to have UE started with a parameter pointing to a different save-map file than the default?

tia
Olav