The STFS/LIVE container method:
Open TU with a Hexeditor and go to offset 0x354. If the first file in the TU (STFS/LIVE container) is a xex, offset 0xD174 may show the same MediaID. There's a Winhex position file attached below.
The XEX MediaID method:
Open the TU with LeFluffie, extract the...