You can move them to another location, where you have enough disk space.
To do this you need:
1) Go to BEUtility.exe (C:\Program Files\Symantec\Backup Exec)
2) Select "All Media Servers", right-mouse click on you server and select "Set job log and catalogs location..."
3) Write the path of your new location.
4) Restart all BE services.
I think that's not a good idea to delete earlier catalog files. Just move them.