After trying for an hour to work this out I then worked out how to restore your files , What you need to do is the following.
This will only work if you have a backup of your data...
1) Open the folder that contains your backup data, from there you will need to copy all folders & files under the Express backup.
2) And copy them to the folowing folder below overwriting all files that are currently in there
3 c:\users\all users\nch sofware\expressinvoice
4 This Folder is a hidden folder so You will need to unhide this if you want to copy it in windows, or you can copy it from a dos prompt if you are unable to find out how to unhide folders in windows Vista
This way does work in Windows Vista, and does not cause any problems