Here, again, is the link to Snopes: http://www.snopes.com/computer/virus/youtube.asp

However, rather than worry about these things, it is far better to do two things instead...

1. Use an effective Anti-Virus program that continually looks for updates.

2. Don't just willy nilly open email attachments. Always be suspicious and apply a little bit of verification to any email with an attachment. Ask: Did I expect the message? Is it directly from someone I know?

I don't open attachments that the sender fails to tell me what to expect. And if I'm not told as part of the sent email, I ask.

Jim