i have a few ways to try, apart from the common one i was thinking, i read this...
1) Download Deamon Tools 3.47 from here.
2) Install Deamon Tools
3) Mount the Vista DVD .iso file by right clicking the lightening bolt icon in your system tray, choose virtual CD/DVD-Rom, then Mount Image, locate your .iso and open it.
4) The Auto-play will start, >!CLOSE IT!<, Create a folder on your desktop and name it Vista Install.
5) Navigate to My Computer, then the drive letter that denotes your new virtual drive, right click it and choose Open.
6) Proceed to copy all the contents from the virtual DVD onto the folder labeled Vista Install.
7) Once all this is finnished and you are sure you copied all the contents from the Virtual DVD, unmount the .iso file you just mounted by right clicking the Lightening Bolt icon, choose Virtual CD/DVD-Rom, then unmount all images.
8) Navigate to the Vista Install folder and double click Setup.exe.
9) Either choose upgrade, or Custom, and select your drive you want vista to go to once your prompted to that point. Setup will continue as usuall.
Will update if i can get it to work...