Check and make sure your friend did really send that great screensaver
A common method of transmitting malware is by infecting some
unsuspecting user's computer and then using that computer to infect
others. One simple way to do this is for a hacker to hijack your
address book and send copies of the malware to everyone in that address
book. Of course, YOU need to be enticed to run the malware, and the
best way to do that is to fool you into thinking the attachment is
something else. If a friend or acquaintance sends you a "great
screensaver" or something similar, which you were not expecting, take a
few minutes to confirm that person really sent it. If they know
nothing about it, then delete the message.