the short answer is not without a new fork, as it's rather difficult to get your fork threader aligned properly on the fork without specialized tools (other than standard shop fare) Also, your star nut will prevent the installation of a standard stem, and the I.D. of the steertube is different 'cuz the wall thickness has to be greater on a threadless fork 'cuz it's gotta take all the load from the stem. I wouldn't really advse it without getting a new fork. That said, a new fork/stem/headset should take care of things provided you're going from one inch threadless to one inch threaded/ 1-1/8 threadless to 1-1/8 threaded.