Install the program as normal following all onscreen prompts.  When you are done, restart the computer if you are asked to do so then right click on the same icon and select enable.   Each anti-virus program has its own terminology so go for the command that fits disable and enable.

If you are running an anti-virus that doesn’t show in the system tool tray, then double click on the icon on your desktop or find the program in your program list.  In XP, click on start, in Vista click on the start logo, then click on All Programs and look for it in the list.   Once the anti-virus program loads you need to look through the various options for something that matches “real time protection”, “live watch”, “live protection” or words to that effect.  There will be an option to disable and some programs even have a time limit to select from.

The key is to make sure the program you are installing is completely installed before re-enabling your anti-virus.

In you’ve already tried installing a program and are running into problems and suspect your anti-virus program blocked part of the install all is not lost.  Disable the anti-virus and try to uninstall the program either through the programs uninstall function or through Add/Remove Programs in the Control Panel.  If that fails then try to reinstall the program over the existing failed install.  Once you have the program installed then re-enable your anti-virus program.