Software will not uninstall

Windows XP SP2. What is the correct way to uninstall software that will not uninstall using conventional methods, ie add/remove programs.
I wasn't getting sound on an AVI file so I installed the ACE Mega Codec Pack Professional Edition. It won't work, giving me an out of bounds index (-1) message when it tries to initiate. Tried to uninstall using add/remove programs and the uninstall path through the program manager both fail to initiate. I've reinstalled so that I can uninstall but that doesn't work either.
Is it as simple as manual removal of the program folder and entering reg edit and removing the software entry. Obviously this will leave the drivers, but...is there another way?

 

HI if you use the uninstall function of CCleaner it is fairly powerful.

http://majorgeeks.com/CCleaner_d5125.html

if that does not work have a look through these programs many with uninstall functions.

http://majorgeeks.com/downloads12.html