All are under HKLM\SYSTEM. I just search and modify until "find again" comes up with nothing. Some of the results are already at zero, and probably represent orphaned keys. Keeping in mind that CurrentControlSet is just an alias for the relevant control set number, these are the locations I expect are actually relevant:
The GUID will vary, and the numbers may as well. I have 0000 through 0006 under the Video path, though I don't know at this point which are actually relevant. I just change all instances of EnableULPS to 0.
It is, of course, possible that your problem is something else entirely, but I find it somewhat unlikely.