Shellmanager Database Issues...

I recently performed a system restore because a friend got on my computer when I wasn't home and went crazy with downloading causing my computer to not run as good as it was. When I went to take off NERO 7 Demo (after the system restore) it says "Shellmanager Database is corrupt or missing." Then it goes on to say "Fatal error during installation" for the add/remove programs. I don't know much about computers. Can someone explain to me what this means and how to fix it? Thank You.

Computer Info:
-Microsoft Windows XP Professional (version 5.1.2600 Service Pack 2 Build 2600)
-Compaq Presario 061 Model: P8657C-ABA 8000z NA530 (X-86 based PC)
-AMD Athlon 64 Processor 3400+
-2.19 GHz, 1.00 GB of RAM