There are several ways that you can do so, but the easiest way I have found is via the use of Process Tamer.
Process Tamer is a donation-ware that runs in your system tray and constantly monitors the cpu usage of other processes. When it sees a process that is overloading your cpu, it reduces the priority of that process temporarily, until its cpu usage returns to a reasonable level.
Using Process Tamer
Download Process Tamer from DonationCoder.com.
Run the installer. (The application works on Windows XP/2K/NT/Vista/Win7)
Once you have completed the installation, run the Process Tamer application. At first run, you will see the window as shown below:
You will be prompted to enter a license key. If you are wondering why you need a license key for a free software, this is because ProcessTamer is a donation-ware and the process to acquire a license is to encourage you to make a donation to support the developer.
To acquire your free license key, go to Donation Coder Forum and register a user account. Once you have created a user account, go to Process Tamer license page. Copy the license and paste to the Process Tamer app.
After the app is activated, it will automatically run in the system tray, monitoring your computer’s CPU usage. This is what you will see when you open the configuration window.
You can see the Priority assigned to individual process. If you see that an application is taking far too much CPU resources, or that you wish to limit a particular app to low priority, you can manually set the “Explicitly Rule” to “Force below normal” or “Force Low”.
On the Configuration tab, the more important thing you should take note is the marker for CPU Trigger Low and High usage. You can set the value to a higher or lower value if you find the default values don’t work well for you.
You can also select if Process Tamer should start on boot up.
Overall, Process Tamer works pretty well even if left alone. You can simply install and leave it and it will do the necessary monitoring. If, however you need to restrict certain apps to have high or low priority, Process Tamer allows you to do so too.