Mountain Biking - newbie with questions

just bought a mtn. bike(diamondback response sport) a couple of months ago with the hopes of getting back in shape while doing something that i used to love as a kid. some of the guys that i work with ride road bikes and run a lot. they have talked me into doing a sprint triathlon in august. alright, that's the background, now on to the questions....i'm doing road training on my mtn. bike. i've looked around for set-up tips on the net and haven't found what i'm looking for. other than changing to rigid forks and slicks, what do i need to do? somebody suggested that i change the cassette, but i don't really know what would be worth my time/money to do. anybody out there done this before? any suggestions would be great.

You'll get in better shape training with a mtn bike on the road. I would definately change tires and try that first. I ride a mountain bike on the road and I never feel like I need higher or lower gears. The thing to do is just ride, as you get stronger you might want to change other things.

You could also even swap to road bars. Seen that a few times on mountain bikes, even for off roading. I'm not a road rider myself though so I can't offer much.

What are you going to be riding in the race?

i'm planning on using the mountain bike in the race. the plan right now is to make all the "speed" changes about two weeks out from the race. i just want to make a few changes to utilize all the energy i'm putting in.

Very good choice of a starter bike.

Things you might want to try are :

Clipless pedals
Smaller tires, less knobby
Lighter Components
Perhaps V brakes (lighter, and usually have less rub = less speed loss)

And maybe, you could try a road cassette. The cogs are made smaller than mountain bike cogs, so it'll be a lot easier to gain speed and keep it.

http://www.bikeforums.net/showthread.php?t=67259