I've installed AoE III without any problem but the game won't launch (or
rather in over thirty attempts it has started twice!) I see the egg timer for
a few seconds but otherwise nothing and then eventual an error box flashes up
which says

Script Exception Win32StubLib (window title)

Error Code: 12
TR_Decrypt: Failed to get transaction encryption key
Param 1: 0
Param 2: 24 (I've seen different numbers here)

I have AMD Athlon(tm) XP 2000+ 1.7 GHz, 1Gb RAM, nVidia GeForce3 Ti200,
DirectX 9.0c and msxml 4(sp2)

Any ideas?