If you use a Windows PC it has a series of files making up what is called the registry. In the registry you can find information about the hardware and software on your PC. When you boot up your PC Windows uses the information in the registry during the startup process. Information in the registry identifies programs that startup. Many of these programs run continuously until you shut your PC down. While your PC is running many programs put things into the registry as well. A classic example is the most recent files list. Many PC programs use the file menu to display a list of the files that you have opened recently. This recent file list is often kept in the registry.

Programs with a malicious intent may put stuff in your registry. Mailware, spyware, and adware will frequently put things in the registry so that when your system starts up those programs will be running. This way can annoy you or worse. They may just bombard you with ads or the extremely evil programs may attempt to steal your personal information, or hijack your PC turning it into a "bot" to send spam.

Most anti-virus programs will locate the more harmful viruses and other programs that install themselves on your PC. But frequently these programs miss the adware, malware, and spyware.

If you know what you are looking for, you can delve through the registry with programs such as RegEdit and MSConfig.

RegEdit is a program supplied by Microsoft that allows you to edit the registry. However, if you make a mistake while using RegEdit to edit the registry, you can mess up the registry, corrupting it to the point that your system may not boot. Or if the system boots if may not operate properly.

MSConfig is a program that is safer than RegEdit that allows you to control what programs and services run at startup.

However, both programs require you to be knowledgeable about what you are looking for and how to remove it or disable it -- without causing any problems for your system. Problemmatic at best!

So the average PC user should probably stick to special-purpose programs. However, I must issue another warning!

It is common for writers of malicious programs (malware) such as adware and spyware to create a program that may even perform its intended task, such as cleaning your registry. But in addition to the advertised function the program may install adware or spyware. These types of programs are themselves adware or spyware. So be sure and carefully investigate any freeware or share programs that you download and install on your PC. Make sure the download site is one that is reliable. Double-check the software vendor's site and perform some internet searches to see if the software shows up on any lists as malware.