Every time I switch on the computer the bt broadband file comes up - how can I get rid of this so I dont have it coming up when I switch on?

Download Mike Lin's Startup Control Panel. (Clean freeware.) There is no installation necessary. It's a standalone porgram.

Find the entry responsible and uncheck it. Restart for the change to take effect.
http://www.mlin.net/StartupCPL.shtml