I did find a program that works with Vista a while ago when I had my old mouse, but since I got my Logitech G5 mouse the software with that does it for you, which also works with Vista.
I'll try and find the software I used to use to do it, it worked fine and was easy to do.
It is safe to do it, but you will notice a slight increase in CPU usage, though it wasn't anything to worry about when I did it. It was hardly noticable.
Edit: Found the program
http://files.filefront.com/hidusbfzi.../fileinfo.html.
This worked on Vista 32 bit and 64 bit for me, but obviously with 64 bit I had to disabled driver enforcing for it able to edit the usb file.
There's a readme file that includes all the instructions to doing it right, and download mouserate to check your speed to see if it's increase correctly.
This only increases it for your mouse, as well.