I downloaded a freeware synth program called Crystal today, but when I unzipped the file all I got was a file called Crystal.dll.
Does anyone have any clues about what I should do with it?

(From) http://www.greenoak.com/crystal/download.html

Installation Instructions

Windows
Download the windows version of Crystal. The name of this file is Crystal.dll
Copy this file to your VST Instruments folder. See the documentation for your VST host for the location of this folder.
Optional additional steps:
Crystal includes 128 patches and 8Mb of sampled waveforms built-in. For additional patches and waveforms, follow these additional instructions:
Within the VST Instrument folder create two folders and name them exactly like this:
CrystalPatchBanks
CrystalSoundFonts
For additional patches, download Crystal patch bank (.fxb) files and put them in the CrystalPatchBanks folder. You will then be able to load those patch banks using your VST host. Alternatively, you can use Crystal's patch bank browser to load them. See instructions for Crystal's patch bank browser here. You can find patch bank files for Crystal by clicking on "Patches" at the top of this page. More great patch banks can be found by joining the yahoo discussion group (See "join the Crystal discussion group" above) and visiting the files area
For additional waveforms, download the 20MB SF2 ROM by clicking here.. Copy this to the CrystalSoundFonts folder. Place any other soundfonts in this folder as well. These soundfonts will show up on the Oscillator Type menu for each voice.

Thanks, Dan. I don't think I have a VST instruments folder. Do I just create one?

No. You'll need to download a VST utility. Here's some info, links, etc.......

http://en.wikipedia.org/wiki/Virtual_Studio_Technology

http://www.soundonsound.com/sos/dec00/articles/vst.asp

http://www.moderato.ns.co.yu/17english.htm

Step by step I come closer... thanks again, Dan.

ADDED - Hmm, starts to look like an expensive hobby. I might stick to Coagula and a couple of other free progs; I'm not aiming to be the next Brian Eno.

One free prog I do like is Saccara:
http://www.visiomedia.com/rooms/offi...cara/index.htm

I sometimes find music distracting when I work at the computer; the melodies get their hooks into my brain and I can't shake them loose. Saccara produces ambient sound that is quite relaxing.

If you're looking for something a little further again from traditional music, try Space Theremin.
http://www.zetacentauri.com/software_spacetheremin.htm