The bad guys are still out there circulating viruses and spyware, so you still have to be on alert.

And this is something that you have to think about as you migrate to Windows 7. If you purchase a new computer, you will find that most come with a trial version of an anti-virus program.

Most manufacturers will give you a three-month trial subscription to an anti-virus program by a major manufacturer, such as McAfee or Symantec (Norton). At the end of the trial period, you are expected to ante up for the full price of the next year's subscription.

That is certainly an OK thing to do -- and it may be the easiest, since you probably won't have to install anything. However, you can accomplish the same type of protection more inexpensively. There are several free anti-virus programs, such as AVG and AVAST.

There is also a new free anti-virus program that has come to the forefront lately. It is the newly released Microsoft Security Essentials program. This is a free download at the Microsoft Web site at www.microsoft.com/security_Essentials.

Security Essentials has gotten a good review from security experts. The program is small and unobtrusive. It uses only 11 mb of disk space.

It is easy to use and to understand. The interface is clean and uncluttered. It protects against both viruses and malware. During everyday use, it is fast and uses minimal resources.

In my trials, I found that scanning was a bit slow, but that is also the case with other free anti-virus programs, such as AVG. And unless you are in a hurry, you won't mind that the occasional full scan takes a little longer.

The name Microsoft, along with the backing of many security experts, makes this program one that a lot of people will use. As you might expect, it will run well on Windows XP, Vista and Windows 7.

When you buy a new computer, sometimes the trial anti-virus software is already installed, and sometimes it is not. If it hasn't yet been installed, you will be asked to install it during the computer setup. If you don't want to install it, you can just skip over that part of the setup.

If it comes pre-installed, you can try it and see how you like it for the trial period. When that ends, you can install this new Microsoft anti-virus program or any other anti-virus program of your liking.

However, you must remember that you should only use one anti-virus program at any given time. So if you decide to change to a different anti-virus program, you will want to uninstall your old anti-virus program first.

To correctly uninstall your old anti-virus program and install a new one, you will want to:

Download or purchase a boxed version of the new program.

Go offline. You can do this by unplugging your modem.

Uninstall the old program by going to the Control Panel and choosing to uninstall it from the list of installed programs using the Add/Remove Program option in Windows XP or the Programs and Features option in Windows Vista and Windows 7. (Click on Start and choose Control Panel. Then make sure that the Control Panel is in Classic Mode in Windows XP or Vista and in the "icon" mode in Windows 7.)

Install the new anti-virus program.

Go back online.

If you are upgrading to Windows 7, you will need to make sure that the anti-virus program that you are currently using will work with Windows 7. You can check out the manufacturer's Web site or Microsoft's Windows 7 Compatibility Center at www.microsoft.com/windows /compatibility/windows-7 to find out if your anti-virus program will work with Windows 7.

A general rule of thumb is that most anti-virus programs that were released in 2008 or 2009 will work. Most older programs will need to be updated.

I cannot emphasize how important it is to have a good anti-virus program installed on your computer. Remember, we all have to be careful out there!

Sandy Berger welcomes all of your questions and comments on today's column. Please post them on the Compu-Kiss Message Board at www.compu kiss.com/happycomputing.