Check if your slash.dll is (565,248 bytes)exactly (there may have been something that tried to alter the file.
Its located in C:\Program Files\Larian Studios\Beyond Divinity\
Are you shutting down all non essensial programs before trying to run <img src="/ubbthreads/images/graemlins/beyond.gif" alt="" /> ?
If you are not sure how to close programs out of your systemtray, you can install this little program
EndItAll and once in the program, click on the button that looks like 2 skulls (or labeled "kill it all"). That will close everything that is running in the background.
Then try again... but thats all i can think of to make the game run on your computer.