I need a toy piano sound. I found a free toy piano VST plug-in, and it seems to be the only one out there that's free. I downloaded it, placed the .dll into the Vstplugins folder, and re-scanned plug-ins from Sonar. But the plug in doesn't show up in the menus when I try to add it from Insert Synth. Something simple I assume? I don't know if it's 32 or 64-bit, I tried a bunch of the folders listed under Options in the Plug-In Manager.

A re-scan may not be enough. It often takes a reset and re-scan. Also if it's free, it may not be written in full conformance to the spec.

free soundfont that come with Sonar Dimension Mini Piano.sfz sound really good here..
 
you just need to load the free soundfont player..

if you tell which plugin it is, others could try (it if it's free)

Placing the .dll into the Vstplugins folder might not suffice - did it come with it's own installer?

Also...it is 32- or 64-bit?