There are 2 ways to fix this problem.
Method 1
A) Uninstall Gnotella
B) Delete any files which might remain in the directory Gnotella was installed in that have the extensions .exe and .dll
C) Reboot
D) Reinstall

or

Method 2
A) Uninstall Gnotella
B) Reboot
C) Reinstall in a different directory than it was previously.

Shaun