My niece’s husband has a computer running Windows XP that, unfortunately, has a virus or malware infection. One thing that is all too common with recent programs attacking PCs is that they reduce one’s ability to effectively utilize antivirus software.
An approach that has promise is to use a “live CD” that boots its own clean operating system, mounts the disks in the computer, and performs an antivirus scan.
I’m downloading and burning ISOs for a couple of such “live CDs” to pass on.
There is the Chronomium live CD. one of the features that I haven’t quite figured out yet is that somewhere one is supposed to be able to also download antivirus definition updates to place on a USB storage device, which is useful if the target machine does not have a direct link to the internet. If a direct link is available via DHCP discovery of IP address, gateway, and DNS servers, the software will automatically find updates on the net.
Then there is the INSERT Security Rescue Toolkit, which promises to fit on just a credit-card sized CD-ROM. It has a number of features beyond just antivirus scanning, and also seems to be set up to go directly on a USB device.