tell application "System Events"
    set the parent_dictionary to make new property list item with properties {kind:record}
    set the plistfile_path to "~/Desktop/MY_DATA.plist"
    set this_plistfile to ¬
        make new property list file with properties {contents:parent_dictionary, name:plistfile_path}
    make new property list item at end of property list items of contents of this_plistfile ¬
        with properties {kind:string, name:"thename", value:theName}
    make new property list item at end of property list items of contents of this_plistfile ¬
        with properties {kind:string, name:"creationDate", value:creationDate}
    make new property list item at end of property list items of contents of this_plistfile ¬
        with properties {kind:string, name:"serialNumber", value:serialNumber}
    make new property list item at end of property list items of contents of this_plistfile ¬
        with properties {kind:string, name:"Email", value:fullEmail}
    make new property list item at end of property list items of contents of this_plistfile ¬
        with properties {kind:string, name:"IPAddress", value:IPAddress}
end tell

set theName to "demo"

tell application "System Events"
    set the parent_dictionary to make new property list item with properties {kind:record}
    set the plistfile_path to "~/Desktop/MY_DATA.plist"
    set this_plistfile to ¬
        make new property list file with properties {contents:parent_dictionary, name:plistfile_path}
    make new property list item at end of property list items of contents of this_plistfile ¬
        with properties {kind:string, name:"thename", value:theName}

end tell