Removing clients viruses w/o thier antivirus

I am generaly a hardware tec. When I go to a clients site, it is usually for a hard parts failure. I want to expand my horizions and income to include scanning thier computer for viruses. Is there any way to set up a disk, CD or Floppy, so I can scan thier computer with the latest antivirus definitions? It would be nice to start with a floppy and then maybe having an extra CD with the definitions on it or something of that sort so I can load this on ANY computer. If someone could help me with basic step by step instructions, I would greatly appreciate it, thanks.