If your looking to use Microsoft Data Protection Manager for MOSS, beware of a little gotcha.
In WSS or MOSS a specified file or folder name has some limits. The URL path for all files and folders must be 260 characters or less (and no more than 128 characters for any single file or folder name in the URL).
Typically you need to think out a folder and file naming convention that suits, and helps stop you falling foul of this. If for example you try to index a file server with longer file names and paths, you'll find your indexer starts to struggle as it cannot actually handle long names.
This also surfaces in DPM which also enforces this rule, so if your trying to protect your data and you have folders that are just a bit too long the DPM sync job will fail.