Organize / Folder and search options turn off Show all folders (you can also access the option by right-clicking on empty space in the left Explorer pane). Now simply pressing Win+E should start Explorer rooted at Computer without the user folder expanded (at least it works that way for me in Windows 7).
You can also change the Target of the Windows Explorer Start Menu shortcut to something like
%windir%\explorer.exe /e,C:\ to open at C:\ instead of Libraries (or whatever the default location is).
Finally, if you want to remove the user folder completely from the navigation pane irrespective of whether Show all folders is enabled or not, follow the tutorial here.