You could always hook up the disk to another computer if possible and get to the files from there.
Or buy another harddrive, install Vista on the new one, and hook up the drive afterwards and get the files. One HD for Windows and one for files is always a good idea, also a third for backup of the second...
Ubuntu Live cd is also an option to get the files, but you'll need another HD to copy the files to.
Maybe there is something wrong with the MBR (Master Boot Record)?
Try Recovery Mode on the Vista CD if such thing?
Anyways, the data is most probably still in there, so in one way or the other, you should be able to get them out again...