Mate that is the startup sound. You must have never used XP.

The startup sound has an upwards melody, the shutdown has a downwards melody. 

 Oh man, you're right. I don't know why I heard it differently before. 

 They are similar but the other goes down in pitch (shutdown) 

 Yea, I could hear it in my head when I read your message. I rebooted that old emachines a thousand times.