Let's try this...
Please download and run this reg file...
http://www.kellys-korner-xp.com/regs...ytoolsundo.reg
Double click to add...say YES if it asks you to merge into the registry.
Post any errors you encounter. If that fails...try the one below...
http://www.kellys-korner-xp.com/regs...reregistry.reg
If you reboot and it's again disabled...we will need to remove the infection that keeps changeing the keys.