I did this with my old Voodoo for commuting
Got all bits cheap from here or ebay cost next to nowt (about £70 I think but the stuff was very good quality, all pretty much as new)works fine, so dont understand what people up there ^^^ are saying, was alot cheaper than buying a comparible spec road bike!
I –
fitted Shimano Tiagra road cranks and B/B (works fine with existing XT mech) to get a higher top gear
fitted cheap Ritchey drop bars, with a 60mm 6degree stem ran with 10mm of spacers underneath they are fine reach and drop wise for the frame, cost about £8 from CRC flood sale I think
Charge bar tape to match existing saddle
Shimano Sora STI brake / gear levers – ran with existing XTR V Brakes via Problem Solvers Travel adaptors
Specialised cross top secondary brake levers for when Im fighting through traffic and not on the drops of the bars
Still have the 26" wheels as frame doesnt have disc mount but running 1" slicks on them
Bike had rigid Pace forks already
Does me for commuting and is noticably faster than same journey on my MTB
Still offroad capable to some extent with knobblies on, it – say round FtD at Cannock or Sherwood Pines, along canals etc, easy stuff it is 'interesting' off road though