Installer cannot update/install

It seems some monitoring programs (anti-virus, anti-spyware, optimisers, etc.) are keeping various installer files open or some services do not stop in a timely fashion.

Best solution is to:

1. Reboot the computer.

2. Uninstall the software.

3. Reboot again.

4. Install the software.

This is not what is expected to happen with upgrades; it is a procedure to ensure the install/upgrade suceeds when issues arise.