I finally got fed up with those asinine sounds SE5 plays whenever you click a button, open a window, or generally use the interface. To me, they make the game feel really cheesy. Thus, I made some 1 ms silence wav files to replace them. They were made by recording a null line-in device, then cutting off all but .01 s of sound in windows' sound recorder. I tried just 0 kb .wav files, but the game raised an exception on them.
With these null sounds, I think my SE5 experience is an order of magnitude more fun...
I think I got all of the offending sounds, but I might have missed some here and there. If so, I can update the zips.
To install the sounds, extract this file into your SE5\Sounds directory, choosing yes to overwrite:
NullInterfaceSounds.zip
I've also uploaded the original sound files for easy restoration of the stock sounds:
StockInterfaceSounds.zip