Ahh, I see what you mean.
All you can do, is reduce the sample rate or bit rate, and all you really need to do that is a sound converter - either Audacity, as Jim suggest, or I find that Wavosaur is pretty good, free, and easy to use, it's an old school wave editor, but it supports conversions, fading, loops, MP3 etc etc, all you need in one free package.
If I was trying to mix looping sound files, well I'd try and optimise them as much as possible, like using as short a loop as I can, trying to stick to a standard length. Also, I would load each sound in, and set the volumes to 0, then play each sound individually. That way, you might not have a timing glitch. If you load a few sound loops, and start them looping all at the same time, then there might be an issue with a delay in queing up the sound file. Often sound engines will wait until the sound is playing before loading anything, so it's best to kick start it by playing each sound beforehand, so it's ready to play with perfect timing.
Health, Ammo, and bacon and eggs!
