Schrullenhaft, thanks for answering my post. I'll endeavour to provide the relevant details:
Windows version: ME (4.90 Build 3000)
Video Card: NVidia GeForce 2 MX/MX400
Direct X: ver 9.0c
Display Driver: nvdisp.drv ver 4.14.0010.8198 (English) - downloaded the drivers from the nvidia site where they're listed as version 81.98.
Both CMBO and CMBB bought from UK sources - the former from Amazon, the latter from Ebay. Is it possible the anti-copy protections on the games are intefering with each other in some way?
Ran Scandisk, no problems detected.
LTD