Not much to it, and it generally works fine for me on Windows 7. If it gives me an error, it's because:

1. It's not in the correct uncompressed CD quality 16 bit 44.1khz format.
2. The sample is TOO SHORT (like a hihat you trimmed away the silence on).

My fix is to open the sample in a wave editor (I use SoundForge). I verify all is correct or even resample it to 44.1khz and change the bit depth to 16 bit whether it needs it or not. If it's a short sample such as a hihat, I'll add some blank space to the end of the file and resave the sample.

The sample then loads fine in Wave Converter.