i installed bd again, wrote the file size down byte by byte (Site Alpha)
copyied the entire install to another directory (site Beta)
started alpha, hit exit
folder of Alpha increased by 20 mb
19.9mb located inside acts/act1/dynamic/
after removing the dynamic files, the filesize is short by ~1mb, 1 new folder (capture) and 11 new files.
after looking through a combined search of both folders for 30 minutes, i reached the end without finding the extra files that the right click properties said were there, along with the missing 1mb.

i'll try the file you suggested and post results here.

in response to:
"I don't think any files are being expanded on start and then re-compressed. It would not make sense to base the copy protection check on any data that will be changed, so anything extracted on startup should just be closed on exit and the original archive/database left unchanged. "

logicly, it doesn't make sence, but what could be happening is the game extracts dynamic files for act1 and doesn't clean them up along with moving them instead of copying them to the dynamic folder. the crash to desktop could be from a request to load a file that isn't there. the 1 mb could be the compressed size and 21mb could be the extracted size (hence the 20mb difference above and 1mb difference below. how the 11 extra files fit in eludes me at the moment.