System Error 5 Access Denied
When copying, moving, or synchronizing files, Beyond Compare gives the message, "System Error 5. Access Denied".
This error typically shows up when copying files from a local or network drive to a network drive. The error is due to file or share permissions.
As an example, you might run Beyond Compare on your desktop, and try to copy files from your desktop to your laptop computer over a local network share. In many cases, the account you use on your desktop computer doesn't have permission to write to the remote computer (the laptop). This creates the "Access Denied" error message.
Run As Administrator (Windows Vista and later)
Right click on the Beyond Compare shortcut and select Run As Administrator. Even if your account has administrative rights, Windows normally runs software with fewer permissions. Using Run As Administrator forces Windows to run an application with full administrative rights.
To always run Beyond Compare with administrative rights, right click on the shortcut and select Properties. In the compatibility tab, check "Run this program as an administrator".
Run Beyond Compare on the Target Computer
To make sure your account has write permission, run Beyond Compare on the target computer instead of the source. This should give permission to write files on the target computer.
Change Permissions on the Target Computer
Change file and share permissions on the target computer to allow your user account write access. Tutorials on changing permissions for several versions of Windows are available at the following links:
MUO: How to Network File Share in Windows 10
Microsoft: File sharing over a network in Windows
Change Firewall Settings
If you still have problems connecting to a network share after checking permissions, it might be a firewall problem. If you have a software firewall on your system (including the Windows built in firewalls), make sure it allows file sharing connections.