VGE-Editor wasn't really designed to work on Windows 7 (hence the V at the front)
I've done a few test on the first Beta x86 build of Windows 7 and it worked okay, but I haven't done any extensive testing on RC1 (which I now use).
If you want to PM me the exact error messages that come up, perhaps I can be of assistance. Bear in mind that VGEE is limited in what it can do, and that I'm working on a brand new program that does much more (but won't be available for a while since I don't have as much spare time as I did when I built VGEE 2 years ago).
As far as I know, you should be able to customize the game shortcuts by navigating to %localappdata%\Microsoft\Widnows\GameExplorer, then figuring out which folder is for the game you want to change. In there you should a PlayTasks folder, which contains a subfolder called 0. You can have up to 5 of these folders (named 0, 1, 2, 3, 4) which contain one shortcut each. The 5 shortcuts are the 5 PlayTasks that you could edit in the Vista Game Explorer. Change the target of one of these shortcuts to add the extra arguments you need.
Hope this helps