set objFso=createObject("scripting.fileSystemObject" )
set objWShell=wScript.createObject("WScript.Shell" )

usrName=objWShell.expandEnvironmentStrings("%USERNAME%" )

strFileToCopy="filename.ext"
strFolder="C:\Documents and Settings\"&usrName&"\Desktop"

if objFso.folderExists(strFolder) then
objFso.copyFile strFileToCopy,strFolder&"\",true
end if