- Download the desired ISO image and save it to an easily accessible location on your hard drive.
- Download the Virtual CD-ROM Control Panel for Windows XP. It's an executable archive that contains 3 files: VCdRom.sys (the virtual cdrom driver), VCdControlTool.exe (the control panel application), and a readme file. Extract those files somwhere handy and run VCdControlTool.exe
- Click "driver control," "install driver", then browse to and select the VCdRom.sys file. This loads the driver for use in Windows.
- Close the driver control window.
- Click "add drive" to obtain an available drive letter for your virtual drive. That drive will appear in the list at the top of the control panel with the message "no image mounted."
- Click "mount," then browse to and select your ISO file. The file will be mounted as a virtual drive at the drive letter you specified.
- You can now use this new virtual drive as you would a regular DVD drive to install Vista however you'd like. VirtualPC recognizes these virtual drives, but you can also install Vista from within WindowsXP if you'd like.