Is there any particular reason you have to partition inside Vista itself ?
If not, why not try Gparted ?
Shutdown, change settings to boot form CD, and try it. Once it is done, go back to Vista.
Get Gparted Live CD. That is free, opensource and will do the work.
Get it from -
http://gparted.sourceforge.net/livecd.php
Credits : All credits goes to the senior member
Nucleuskore who posted details in this forum many times.