To reset your graphics settings manually, open up your "Run" dialog (<Windows Key> + R will do this for you) and type in regedit.exe. Click Okay and the Registry Editor will open up.
On the left side of the editor, you will see a hierarchy of registry entries, navigate along this path:
Highlight the Graphics Settings entry in the left pane and delete it. Confirm that you want to delete this key and all of its subkeys.
At this point, try running Xulu again and your display will be reverted to low-end, safe settings.