Joyce V's computer is having trouble with security programs--a strong indication that her computer may be infected with malware. Malware, once it has infected your PC, has a way of protecting itself. It may not want you to install a new antivirus program--or update your current one. So you need to scan your hard drive in a way that gets around the malware. The simplest way to do that is to do the scan outside of Windows.
Luckily, there are several bootable malware scanners. You put one of these on a CD or a flash drive, boot from that, and scan your hard drive. If they find something, they'll remove it.
I'm recommending
Kaspersky Rescue Disk and the
F-Secure Rescue CD, because they're both easy to use and come from companies that have done well in testing. If you're really worried, use one, then the other.
I strongly recommend that you use a different computer to download and prepare these programs. And no, you can't simply burn the files to a CD or copy them to a flash drive.