In most cases, it is required to reboot the computer after each driver is installed. Normally, the installation process will indicate if and when this is necessary.

If you are installing multiple drivers, it is a good idea to restart between installations.  This lets you check that there are no issues related to a specific driver being installed.  If you do encounter any problems it will be much easier to determine the issue and you will only need to revert a single driver to resolve the issue.