Russian webmasters over at Overclockers.ru seem to have found a way to mod currently selling Duron processors into Athlon XPs by locking L2 bridges. If you can read russian, you can find the original article here, if you don't x-bit has an english translation here.
As with most hardware hacks, not all processors are guaranteed to work well with the mod, if you are lucky enough however Durons may function well with re-soldered L2 and functional 256KB L2 cache.