Right-click the shortcut you want to change, change the 'target' field to:

%SystemRoot%\explorer.exe /e, d:\myfolder

If you want to have Explorer start at My Computer, without drive and folder branches initially expanded, in the string mentioned above you replace the part ( /e, d:\myfolder ) with this instead: /n, /e, /select, c:\

To launch Windows Explorer so that it points to the Desktop use this string in the Target field:

%SystemRoot%\explorer.exe /e,%USERPROFILE%\Desktop