2 instances of Xcode installed? I originally installed Xcode via Apple's developer website (not through the App Store). Later on, I installed Xcode via the App Store.

Now in Launchpad, I have two icons for each of these apps: Xcode, Instruments, Dashcode, and Quartz Composer. None of the icons have an "X" button to remove them from Launchpad.

Questions:


Does this mean that I have 2 versions of Xcode installed?
If not, how can I verify that I only have one version installed?
How can I know which file each Launchpad icon is referencing?
If it's purely a cosmetic thing, how would I get rid of the second set of icons? (And does it matter which set I get rid of?)


Update:

I see that the /Developer folder contains an Applications folder, but it also contains SDKs, Documentation, Platforms, etc.

My /Applications folder contains the folder Developer. Inside of /Applications/Developer, there are 4 aliases which link to the /Developer folder. For example, the Xcode alias (/Applications/Developer/Xcode) links to /Developer/Applications/Xcode.app.
If you have the latest Xcode (4.3.2 at time of writing) it should be in /Applications/Xcode. You may have an older Xcode in /Developer. /Developer is now no longer used by Xcode. You should remove it using the provided script if you don't need the old version any more. Execute 

sudo /Xcode4/Library/uninstall-devtools --mode=all


and authenticate. When that script completes you can remove the /Developer folder entirely but you should allow Xcode's script to take care of its somewhat "fragile" installation first.

New Xcode lives in /Applications and is much more like a conventional Mac OS X app these days. Lots more information about putting it in the dock, finding other developer apps, command line tools etc. in this other answer of mine.