Try deactivating the inidisplays and iniwxr plugins from the plugin menu in xp. Be warned you will lose terr radar and wx radar though. I also recently encountered a bugged nd that I think may have been caused by me turning off the displays plugin. However I have completed a good few flights with both off and have had no issues. I gain anywhere from 3-9 fps with them off. Turning off inidisplays may break your screens but like I said it only happened once out of a dozen flights so might be worth a shot if you are really struggling.