"Trojan Horses are impostors--files that claim to be something desirable but, in fact, are malicious. A very important distinction between Trojan horse programs and true viruses is that they do not replicate themselves. Trojans contain malicious code that when triggered cause loss, or even theft, of data. For a Trojan horse to spread, you must, invite these programs onto your computers--for example, by opening an
email attachment or downloading and running a file from the Internet. The PWSteal.Trojan is a Trojan."
Not sure then how you could have got it. Are you sure it was a Trojan. Also virii can be on floppy dsic etc...