This page is for the original release. For the Director's Cut, see Deus Ex: Human Revolution - Director's Cut.
The file naming convention appears to be this:
HKEY_CURRENT_USER\Software\Eidos\Deus Ex: HR
00 00 00 00
Some users report that the mouse feels laggy and looking around feels unnatural. Some have attributed this to an implementation of mouse acceleration, however Eidos developer Jimo has stated that there is "no mouse smoothing applied in DXHR".
Other users, under the impression that the game implemented mouse smoothing, seem to have found a registry setting that modifies mouse behavior and have had some success with editing it to fix mouse lag. Edit this specific registry setting (Be sure to back up your registry before making any changes):
There are multiple solutions that people have reported work:
Some users have reported a drop in fps that continues until the game is closed. 
Other users seem to have found a registry setting that has had some success with fixing the FPS issue. Edit this specific registry setting (Be sure to back up your registry before making any changes):
If your game crashes when a tutorial pops up and only shows black, go into the game options and disable tutorials.
You are more than likely experiencing microstutter. To fix this, disable your 2nd/3rd monitors in windows. So that you only are running one monitor.
If you own an AMD Bulldozer CPU and the game is laggy (or the audio is stuttering), you can download and run a program called Orochi-Ceg that may fix the issue. It should be noted that this solution is temporary and that it may have already been fixed by your motherboard manufacturer. You are recommended to search for a BIOS update on their website for a permanent fix.
You should not, in any case, run this program if you have an Intel processor.
There are modified unofficial BIOSes that you can run that may also fix the issues. Use of these BIOSes are at your own discretion.
GA-M68MT-S2 (3.x) - FCd
Some users have discovered an issue where the HUD moves itself to the left-middle of the screen, as though it were placed for a different resolution. Although a restart of the game usually fixes it, this may not be the case for everyone. This thread, on Eidos' forums, details a number of other fixes users have tried, successfully, to remedy the fix.