Have you ever ran into a situation where you go to install AutoCAD and it acts as if it is already installed but is not actually installed.

If this is the second time you are installing on the PC, In most cases the Installer rolls back and sets everything back to the way it should when you start the Installer. However in some cases this does not happen.When you try to install AutoCAD it acts as though the product is already installed.

To reset the installed we have to remove some registry entries. Before proceeding backup the registry.

In case the problem occurred when the last installation was aborted before completion, then search for these paths in the Registry

HKEY_CLASSES_ROOT\Installer\Products
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Installer\UserData\S-1-5-18\Products
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall

Under each of these look for the Product Name and remove any keys from the GUID level. We can simply search the entire registry for values that points to non existing installation and remove them.

If the install log shows that the install initialization is detecting the existence of a .mst file and cannot proceed because the .mst file. then search the registry for string of the .mst file name and delete that key from the GUID level.

If the log file says the failure is due to custom action, CheckForACADExistance, then browse to the installation directory , usually C:\Program Files\Auto-desk\auto-CAD and remove the auto-cad directory.