What operating system is share running on?
for XP you could go to Administrative Tools, Computer Management and kill open sessions and open files.
It's probably in similiar place in Windows 2K and I completely forgot how to get there in Windows 9x., but I know it's there.
attached is a screenie for XP and probably 2K.
EDIT: When i get to work i'll post Win2K if it is different.'
EDIT#2: Never casually use this option. Depending on the state of the file at the moment of truth, you could have some corruption within the file and/or loss of data. With that disclaimer aside, i've never had a problem doing it

All kidding aside, best of luck!