How do I change where Steam installs to? [duplicate]

I had a problem with Steam a while ago and had to re-install it. When I re-installed I somehow set it to install on my desktop and it cluttered my desktop with all of the files. I moved all of files into one folder and started up Steam, and on starting up it created all of the files again on my desktop after I had just moved them into one folder. I know the default install is C:\Program Files\Steam but mine is set to my desktop, so is there anyway that I can change it back to there without having to re-install?

When you install a game from your steam library the following will appear:

Select the drop down box titled: Choose location for install: and you can select from steam locations, or create one on drives without one already.

You can alternatively manage your Steam library Folders from the steam settings, under downloads:

Click the first button that says STEAM LIBRARY FOLDERS under the heading: Content Libraries and from here you can set up the locations you want to install to.