Hello all, the solution to those who get 'Target box not valid' etc. is:-

PLAYBACK
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"C:\Program Files\Total War\Shogun - Total War\ShogunM.exe" mEP

RECORD
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"C:\Program Files\Total War\Shogun - Total War\ShogunM.exe" ER

The parameter has to be OUTSIDE the quotes!

Open Windows Explorer or (My Computer etc.) and go to the "Shogun - Total War" directory and make the shortcut from the actual ShogunM.exe file, edit it, then use that to run the program.

It didn't seem to work from the desktop icon - might be my computer or maybe windows doesn't accept parameters from the desktop.