Schrader tubes in Presta configured Rims? My 26" mtb rims support presta sized tube stems, however can I drill the diameter of the holes in the rims bigger in order to support Schrader stemmed tubes? what is the proper way to do this, is there a kit?

Drilling out your rims will reduce the strength of the rim and increase the likelihood of cutting the valve stem on your tube. For a few dollars you can buy two of these:

!Schrader Valve Adapter

This adapter threads onto a Presta valve and effectively turns it into a Schrader valve. Presta valve tubes are the same price and are as widely available as Schrader valve tubes, so you shouldn't need to drill out your rims. (Also, depending on how deep your rims are, finding Schrader valve tubes with valve stems long enough could be a challenge.)

For a discussion of the virtues of Presta v. Schrader valves, check here.