Computer programs are never perfect. Millions of lines of code will inevitably contain flaws that may cause the program to perform differently than expected, or even open up security vulnerabilities. Fortunately, individual lines of code can be changed without re-writing an entire program. That's what "patches" are about.
Most people use software that was either pre-installed on the computer when they got it, or came on a disk for them to install. Many times, though, you are getting the original version of the program, and there may be updates, or "patches" available. Some programs even have a patching system built in, where by clicking a link or selecting a menu option, you can have the program automatically check to see if a patch is available, and update itself if there is one.
Checking for patches should be a regular practice. At least once a month, you should visit the web sites of the major programs you use to see if there are any updates available.
Microsoft Windows is a major target of viruses and hackers, mainly because it is widely used by people who know little about security and software flaws. To make the delivery of patches easy, Microsoft has created the Windows Update website. This website can automatically scan your computer to see what version of Windows you are running, and what patches you have already installed. Then, it will present you a list of the available patches and updates, and allow you to choose and install them directly from the site. Some of the patches can be installed in groups, while others must be installed alone, so you may have to visit the site several times to get them all. http://windowsupdate.microsoft.com
Microsoft Office is another widely-used, and widely-targeted system. Similar to Windows Update, there is an Office Update web page at http://office.microsoft.com/officeupdate. Note that you may need to have your installation disks handy during the updates.
For other software, you can go directly to the manufacturer's website if you know the address, or simply use a search engine to find support for that program. Searching on the exact name of the program will usually help you find the creator of the program. Check for a "Support" section of their website, and see if there are any "Downloads", "Updates", or "Patches" available.
When installing a patch that you download from a web site, check to make sure that the patch applies to the version of the program that you are running. Usually, a program version is expressed in a number, such as "Version 6" or "Version 7.2". The decimal numbers often indicate a patch that has been applied, so you might download a patch for a program that upgrades it from version 5.0 to version 5.1. Don't worry too much if you skip a number (such as going from 5.1 to 5.3), just remember that the higher the number, the more recent version you are using.
Major version number upgrades (such as version 5.3 to version 6.0) are usually not made available for free - they require a separate purchase.
If multiple patches are listed for a particular program, the best procedure is to install the patches in the order they were released. Sometimes a recent patch depends on an older patch being installed, so it's important to get them in the right order. Occasionally, though, a specific patch or "Service Pack" will include all previous patches. If that is the case, then you only need to install the latest one to get the benefit of all of them.
If you ever need to re-install your program for some reason, you will need to re-apply all the patches as well. For this reason, it's a good idea to save the files you download in a specific location, so that you will not have to go find and download them again in the future. These files take up additional hard drive space, of course, so you will need to take that into account.