Can my wifes trek hybrid be fitted to work as an ok xc bike?
 

Before I go out and by a new mountain bike for my wife, then find out she hates it. Could I take her hybrid Trek 720 and get a front suspension put on? It looks like an ok setup for going on some trails, it does say multi track on the frame.

I've ridden light trails with people who were on Trek 720s. Of course this was over 10 years ago and maybe the definition of mountain biking has changed. Back then, we were all riding hardnose/hardtails in just lycra and not really doing 20 foot drops. I'm not sure about the specific design or year of your wife's 720 (I think they changed it sometime in the mid-90s) but the ones I used to see were high-end touring machines with drop-bars, wide capacity MTB rear der./gearing (usually DeoreXT), 38/42 double chainrings and canti-brakes. They were actually closer to a cyclocross bike. For offroad riding, people just swapped to wider tyres. The frames were plenty tough.

Actually, I'd have to say most of my riding at the time can be considered offroad cyclotouring. My friends and I would attempt to find as much unpaved trails between small towns and spend the summer riding them. We'd camp out in cornfields and such. Looking back, I'm glad we never got shot at by farmers.

As long as the trail isn't too technical a hybrid should be fine and you may not even NEED suspension. But if you want it anyway, most (maybe all?) hybrids have suspension-ready geometry so making the switch shouldn't be too hard.

Agreed. For most recreational and transportation cyclists, suspension is superfluous.

She purchased it new around 1997. I was thinking suspension for the simple idea of enjoyment. If Im riding my hardtail with suspension, I would like her to have that option, also to maybe allow for rougher trails that will make it somewhat enjoyable for me as well.