is it a virus

Just repaired a computer. The customer, on the 04/02/2005 opened up an email attachment, within seconds the computer had a blank screen. I have never come across this before. The computer itself has completely lost its directory. I have been informed tonight by the customer, that their friends computers have all crashed with the same symptoms after opening up this attachment. I will let you know the name of this attachment when i have more information. I can tell you it was something regarding a “jpg”.