I know what you mean. I only have 1 Vista machine and that's my new HP9700 laptop. I spent a long time making it a dual boot Vista/XP system (1 OS installed in each hard drive) and it was a real pain in the butt with HP actually listing the wrong XP drivers on their site, having to buy a USB floppy is order to install the SATA drivers for XP to install (it was either that or make a slipstream XP disk), chase up beta video driver from nVidia and then finally discover that there are still no audio drivers available! In the end, I wiped the XP install off in frustration.
To be honest, I'm doing OK with Vista now that I've set it mostly for "classic" operations and disabled a lot of the bells and whistles.
My major gripe is the endless:
This program needs permission to run...
You must be a Administrator run run this program...
Are you sure you really want to run this program?
Are you absolutely sure you want to run it ebcause M$ hasn't approved the software?
This is your last chance, do you really want to do this?
OK, we'll allow it to run, but we really think you shouldn't.
Fine, ****ing run it then! See if we care!
:-D