Old-fashioned email programs which just read plain text files could not be affected. For more information on this virus see the Symantec page on Bubbleboy and the Microsoft page on Bubbleboy . This virus appears to have originated in Argentina and was sent directly to anti-virus vendors by the virus author. Passing on email chain letters is generally discouraged. See the CIAC's page on chain letters for information on this problem.
Many chain letters are also hoaxes.
For more on this hoax see the CIAC hoax page and a statement on the Microsoft web-site . There are a number of similar hoaxes offering rewards for forwarding email. But in at least one case there were more serious repercussions. See a report on this case . So at the very least, think about what you are forwarding.