I had to format my H D due to a virus. Saved all data and photos from the H D but lost the catalog with the tags. I reloaded the Photoshop 9 program but it cannot find the former catalog. Is it lost forever or is it in a hidden file? Any help appreciated.
You say : "Saved all data and photos from the H D".
That means you have made a copy of those files. But you don't say anything about the catalog, which means that all the contents of the catalog are now lost.
The catalog is a special folder containing all the information about your files, their location on the drive, their exif properties, all the tagging you have done.
To find where it is located, in the Organizer use the menu Help/system information. That location is always omitted when you 'save all data and photos'.
Another advice in your situation would be to 'write metadata to files' from the catalog manager. Your tags and added information will be written to the pictures files. If you re-import those files in a new empty catalog, they will be recovered. You'll get back: tags, notes, captions, ratings. You won't get back: albums, stacks, version sets, projects.