Hi creativemesh and welcome to the vista forums
You will probably need to take ownership of the folders or drive that the backup files are held.
This is because when you re-installed vista although you main user may be called the same as the previous install in reality it will have different security identity. vista will still recognise that the files are owned by the original user but not recognise it and therefore give the error you receive.
have a look at the following tutorials, take ownership of the backup data and give your new user at least read access
Take Ownership of file - Vista Forums Folder permissions - Vista Forums
Hope this helps