WIN 81 HOST + WIN XP GUEST + SHARED FOLDER ACCESS PROBLEM

[SU127001]

VirtualBox Version
4.3.10
Extension Pack Installed

OS Host
Microsoft Windows 8.1 with update
64-bit

OS Guest
Microsoft Windows XP SP3
32-bit
Guest Additions Installed

Application
MYOB Accounting Plus v9
Legacy Application
16-bit

When accessing MYOB Accounting Plus v9 data files from the host, the application errors with
"Unable to open file; the file may be locked or in use, or access privileges may be incorrect."

Created a new folder on the host desktop and copied the data file to the new location.
Attempted to open the file from the new location on the host from within the application but again encountered the error above.
Checked read only permissions on the data file and parent folder but they appear fine.
Able to read and write other basic files such as .txt from and to either location without issue (users/documents).
Able to copy the data file from the host to the guest and then open that file from within the application without any issues.

Any help or suggestions on how to overcome this problem would be appreciated.
I would guess creating a natural network share on the host for the guest without the installation and support of the guest additions would not be possible.
Thank you.

[BillG]

Why would you think that normal Windows file sharing would not be possible? I never use the shared folders option, I always use Windows file sharing.

All you need to do is observe the normal requirements of Windows sharing. Do you have a network connection between the two machines (Host Only or bridged)? Are the machines in the same workgroup?

[socratis]

Legacy Application, 16-bit

The "16-bit" part might also be another issue. You definitely would want to map your Windows network share to a drive, and even then you might have issues.

[SU127001]

@billg
I wasn't using bridged networking and read somewhere that the guest additions was a requirement for sharing to work properly.
I deleted the virtual machine and recreated it without using guest additions and changed the networking type to bridged and sharing worked just like you said it would.

@socratis
I hear you about the 16bit application but here's an update in my attempt to solve this problem.
Using bridged mode in the virtual machine for networking and creating a mapped network drive on the guest pointing to the host where the data files are stored, I can actually create a brand new accounting file from within the application and save it to the network share on the host without a problem. I can then close the application and reopen that same file from within the application without a problem.
This tells me something is not sitting right with the previously saved data files.
I am willing to bet I can copy each data file to the guest and then open and save each file to the network share on the host and then watch my access problems disappear.
I verified the permissions on the newly created accounting file thinking maybe that would be key but I don't see where any of the security or sharing permissions differ. Maybe some kind of bit or flag value that was previously embedded into the preexisting files is causing this problem.
I will keep researching the permissions but it looks like the only way to solve the problem is to move forward with the method I mentioned above.
So unless anyone else has any ideas...
Thanks.