When you say, "I have a tree on shared disk between two PCs," WHERE is the disk? In one of the two computers? How does the other on access the file?
On a Network Attached Storage device which both computers mount as a drive?
More details on how this 'sharing' is done? Two computers cannot have the same file open at the same time. Trying to do so creates monster problems unless one has the file in a read-only state...even then, what happens if the B computer changes the file while it is open on the A readonly computer? See? it gets really dicey.