Hi zoomzoomam,
Like mansrman says, you may need to reinstall with the Dell disk.
Dell have been sending reinstall dvd's that seem to be pretty much straight copies of the MS dvd (with some ranges anyway).
If you have one of these, you may be able to save your existing files into a folder called Windows.old.
To do this , when you get to step 10 of the tutorial, do not select Drive Options ( advanced ) and do not format the partition. Simply click on the partition you wish to install Vista and with any luck , it will ask if you want to save all the files currently on that partition into a Windows. old folder. You will then be able to access them from your new Vista installation. You will still need to reinstall your apps. and set up the o/s as before.
http://www.vistax64.com/tutorials/117366-clean-install-full-version-vista.html
Or you might try this, which you download as an .iso file and burn to cd as a bootable .iso
EASEUS Disk Copy: Free Disk Copy, Partition Copy Software. Sector by Sector for hard drive backup tool.
You can use isorecorder to burn it to a cd
ISO Recorder v3
Hope that helps
SIW2