Some users, that use Vista and even ones that don't have been reporting a "fatal error" upon loading BC.
To fix this issue simply install BC 1.0 as usual but add the following step:
1) Download /brokencrescent.com/Download/QuickFixes/vista_fatal_error_fix.zip
2) Unzip file into C:\Program Files\SEGA\Medieval II Total War\ and replace the existing .cfg file.
All credit goes to loet66 for fixing the recurring vista crash.