Installation

You can safely install on top of your current version. The installer will detect when it is necessary to uninstall the older version first, and it will offer to do it automatically. This is usally only needed when there have been some big changes, such as added or removed components. In most cases the existing version can be upgraded directly and all your settings are preserved.

No, that is not required. Simply click 'No' to keep your existing software.

It is however highly recommended to uninstall other codec packs. This to avoid problems and keep your system as clean as possible.

This means the installer tries to replace a file that is currently in use by another program.

Close all programs that are active and click on 'retry'. If the same error keeps appearing, then just click on 'ignore' and let the installation continue.

No. You have to uninstall the whole codec pack. Then install it again with only those components selected that you want.

You can however disable (and re-enable) all codecs and filters using the Codec Tweak Tool. This will not uninstall the codecs, but it will effectively disable them.

Yes.

The uninstaller will properly undo all changes that the installer made to your system.

This registry error will occur when the security permissions for a registry key are incorrect.

To fix the problem, open the Registry Editor:
Start -> Run -> regedit.exe

In the Registry Editor, navigate to the key that gave the error. Right-click on that key and select 'Permissions'. Then make sure that the Administrators group has 'Full Control'.

Microsoft:
This is the default splitter. It sometimes has problems playing incomplete and truncated files.

LAV:
The advantage of this splitter is that it contains a stream switcher. That is useful for playing AVI files that have multiple audio tracks (which are quite rare) in players that don't contain an audio switcher themselves, such as WMP and Media Center. It also has good handling of strange and broken files. This splitter is used by default by MPC-HC.

Haali:
It sometimes has problems playing incomplete and truncated files. This splitter also contains a stream switcher.

The solution is to install the exact same version of the codec pack on top of your current installation. That will recreate the missing file, allowing you to uninstall again.

The system restore function of Windows may cause the file to go missing. System restore should only be used to fix your system in extreme situations, such as BSODs or driver issues. You should never use it to undo changes that can easily be undone otherwise, such as removing software.

The solution is to remove the file and then install the exact same version of the codec pack that you currently have installed on top of your existing installation. That will recreate a proper .dat file, allowing you to uninstall.