Before you bug out, look at your hubs. if they ain't original, they might be disc-ready. Most common is the 6bolt design, which'll appear as 6 holes in the non-drive side of your hubs. Shimano makes a center-lock version; if there's a weird lockring doodad on the non-drive side, then they're disc-ready. There are soooo many disc-wheels on the market; if you tell us how you ride and what your budget is like, we can steer you in the right direction.

If you don't have a lot of cash to spend, you'll wanna do what they recommended above and get some SD7 rim brakes. You don't wanna skimp on wheels, as you won't save an $$ in the long run.

-rob