Hyperthreading Problem

Last night I went into setup and turned on hyperthreading on my 2.8ghz Precision 530, and I booted the computer up and windows recognized new hardware and installed it and said i needed to restart. Now it wont go into windows. Its failing everytime and in a constant loop of the Dell flash screen and a flickering monitor. I went into setup again and turned hyperthreadin off, but it has done nothing. I cannot use the Last Good Configuration nor Safe Mode. Does anybody know what I did to my machine?