Hi guys. The given solution works for drives, but I prefer my computer to be on the very top, here's how...
Convert the following plist to XML using terminal:
plutil -convert xml1 ~/Library/Preferences/com.apple.sidebarlists.plist
Edit the plist:
open ~/Library/Preferences/com.apple.sidebarlists.plist
Find in the hierarchy Favorites >> VolumeList and then look for:
<key>Name</key>
<string>Computer</string>
Look immediately below that for the visibility key and change the string from NeverVisible to AlwaysVisible:
<key>Visibility</key>
<string>AlwaysVisible</string>
Close and save
Convert the plist back to binary:
plutil -convert binary1 ~/Library/Preferences/com.apple.sidebarlists.plist
Relaunch the Finder:
killall Finder
Tada! Hold Command and drag the items in the Sidebar to get your computer on top, where it should be.