Try Jingle Palette.

• It's free.
• It supports various audio files.
• And, in my experience of using it, it's very stable.

if you can beg borrow or steal a mac, qLab is free, awesome and virtually industry standard for theatre.

also try SoundByte from www.blackcatsystems.com been using that for years for very same thing. also v stable and very intuitive, maybe even a bit simpler than QLab and less cluttered during a show.

it allows click to play, hot keys, midi trigger, or playlist play. you can also loop individual carts if you want say a birdsong bed under other fx etc.

also features individual level sliders for each cart.

hth

paul d

Or just Ableton Live! Can do everything!

Here's a simpler application for just playing sounds from the the same company that makes Qlab.

Qcart:

http://figure53.com/qcart/

But I'm afraid thats only mac too. If you don't find anything similar for PC I would definitely go for Ableton Live. I've been using it a lot for theater sound design. Lots of possibilities to change the sound live, allows me to change parameters in ambient sounds and at the same time easily play short effects with just a click. And I can do my design while playing along with the actors, no need to render new files after every change. Try it!