Do not reboot the computer, send e-mail or try and remove the virus yourself. Even though an anti-virus software package such as McAfee or Norton may remove the virus at your request it can still leave you with damaged or corrupted files that may continue to cause you problems .
Some viruses attach to files so when the infected file executes, the virus also executes.
Other viruses sit in a computer's memory and infect files as the computer opens, modifies or creates the files. Some viruses intentionally change the behavior of your system by modifying files, by displaying odd messages or by performing malicious acts. Since these types of viruses identify themselves in some way they are usually discovered and dealt with quickly. A virus need not intentionally change the behavior of your system. Neither symptoms nor damage are essential in the definition of a virus.