I have a Dell Multimedia Keyboard, similar to this one:

It has many non-standard keys, like the small circular ones across the top, and the "Multimedia" keys above INSERT/HOME/PAGE_UP.

They can be rebound through simple registry entries. Some sample ones are included below:

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\AppKey]

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\AppKey\15]
"ShellExecute"="C:\\Program Files (x86)\\Mozilla Firefox\\firefox.exe http://mail.google.com/mail/#inbox"

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\AppKey\16]
"Association"=".cda"

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\AppKey\17]
"ShellExecute"="C:\\Windows\\System32\\SnippingTool.exe"

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\AppKey\18]
"ShellExecute"="calc.exe"

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\AppKey\7]
"Association"="http"

I've rebound the "MAIL" key to, instead of booting Outlook, to booting Firefox directed at my G-Mail account. I've rebound the button that would normally open "MY COMPUTER" to instead boot the Windows 7 "Snipping Tool", something I find very useful.

Now, I'm looking to do some other things that I don't already know how to do. Note that answering this question doesn't necessarily require any knowledge about the keyboard or rebinding the keys: I can add, for any given key, a "ShellExecute" entry, and it will simply execute the following command as if it was typed at a Command Prompt. (I'm aware I dumbed that down rather significantly, but bear with me. I'm not really a Windows guy myself.)

I use the volume knob for it's intended purpose, to change volume. I would like to change, however, a different key, to "reset" the Windows volume level back to exactly 50%, or, as it refers to it, "50", on it's 0-100 scale.

I'm looking for the "program" (what I would type at a command prompt? these are still just Sys32 programs in the PATH, aren't they?) that, I imagine, would take arguments, to change Sound/Volume settings under Windows 7. Perhaps, for clarification, something that might take the form "C:> SetVolume -slevel 50" or something.