APPID: Error 2727 - The directory entry 'ACADDIR1' does not exist in the Directory table.

 This error appears on workstations with a combination of the following

AutoCAD applications installed:

AutoCAD Mechanical

AutoCAD Architectural

AutoCAD P&ID

And

AutoPLANT P&ID SS2 Versions

Error 2727. The directory entry 'ACADDIR1' does not exist in the Directory table occurs either on install or during the uninstall.  We will try to outline the solution for both instances:

1. Uninstall all AutoCAD applications.
2. Run a registry cleaning utility such as CCLEANER.EXE.
3. Manually remove the Bentley Applications by manually searching and removing all instances of Bentley from the Registry (Export out for backup purposes) and all Bentley related folder and files on the workstation. 
4. Manually remove all AutoCAD Registry entries ((Export out for backup purposes).
5. Removing AutoCAD Entries in Registry:

Make a backup of HKLM\Software\Autodesk and take a look at HKLM\Software\Autodesk\AutoCAD\rx.x\* and delete any subkeys directly below rx.x that are not actually for valid instances of AutoCAD.

For instance, if there is a key like:

HKLM\Software\Autodesk\AutoCAD\R18.0\NavisWorkStuff

Delete the NavisWorkStuff key.

Likewise, if you have something that looks like a valid instance of AutoCAD, but it is not actually a version that’s installed on the machine, delete it.

So if you see HKLM\Software\Autodesk\AutoCAD\R17.0\ACAD-4001:409

But no version of R17 is actually on the machine, delete it, as it’s a phantom registry key for an AutoCAD version not installed on the machine.

1. (Step needed if error is received during uninstall)  Manually remove the Bentley applications from the Control Panel > Add Remove Programs List by taking the following steps:

How to manually remove programs from the Add or Remove Programs tool:

Link: http://support.microsoft.com/kb/314481

Click Start, and then click Run.

In the Open box, type regedt32, and then click OK.

In Registry Editor, locate the following registry key:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall

In the left pane, click the Uninstall registry key, and then click Export on the File menu.

In the Export Registry File dialog box that appears, click Desktop in the Save in list, type uninstall in the File name box, and then click Save.

Each key listed under Uninstall in the left pane of Registry Editor represents a program that is displayed in the Currently installed programs list of the Add or Remove Programs tool. To determine which program that each key represents, click the key, and then view the following values in the details pane on the right:

DisplayName: The value data for the DisplayName key is the name that is listed in Add or Remove Programs.

-and-

UninstallString: The value data for the UninstallString key is the program that is used to uninstall the program.

After you identify the registry key that represents the program that you removed but which is still displayed in the Currently installed programs list of Add or Remove Programs, right-click the key in the left pane of the Registry Editor window, and then click Delete.

Click Yes in response to the "Are you sure you want to delete this key and all of its subkeys?" message.

On the File menu, click Exit to quit Registry Editor.

Click Start, click Control Panel, and then click Add or Remove Programs.

In the Currently installed programs list, verify that the program whose registry key you deleted is no longer listed.

Do one of the following:

If the program list is not correct in Add or Remove Programs, double-click the Uninstall.reg file that you saved to your desktop in step 5 to restore the original list of programs in the registry.

-or-

If the program list is correct in Add or Remove Programs, right-click the Uninstall.reg file on your desktop, and then click Delete.

1. Search the registry for the following:  AutoDESK, AutoCAD, AutoPLANT, P&ID, PID, REBIS. 
2. Remove any invalid entries.  In this case if AutoDESK and AutoPLANT are all uninstalled then anything in the registry should be invalid.
3. Reboot workstation.
4. Reinstall AutoCAD. Open and test AutoCAD native drawing.
5. Reinstall AutoPLANT P&IW and P&ID.