def guid_to_string(guid)
    aguid = guid.unpack('H*')[0]
    sguid = '{' + aguid[6, 2] + aguid[4, 2] + aguid[2, 2] + aguid[0, 2]
    sguid << '-' + aguid[10, 2] + aguid[8, 2] + '-' + aguid[14, 2] + aguid[12, 2] + '-' + aguid[16, 4]
    sguid << '-' + aguid[20, 12] + '}'