Originally Posted by Dirtdrop
I've seen it done. There was pleanty of room for 700c's on a mountain bike frame designed to accept huge knobbies. This bike had road side pulls installed. The only thing I didn't like was that the studs for the cantilevers were still there.
The frame has to be cold set to accept a narrower road hub. but that's no big deal. The special tools required are a 2X4, a piece of string and a ruler.
The OP said he wanted to convert an old road bike to a 29" mountain bike, and the next poster said it might be possible to convert a frame originally intended for 26" wheels to 29." I'll say again: can't be done, and I only listed a few of the reasons, there are more, particularly in regard to the road bike to mountain bike conversion.
edit: Dirtdrop, if you mean converting a 26" wheel mountain bike frame to use with 700c ROAD tires and hubs, then that's a different thing. But that's not what was being discussed.