NORTON IS NOT GOOD FOR MOST TROJANS!
What is the name of the trojan you have?
Do you run any spyware removers...such as spybot or ad-aware?
If it isn't average spyware i like moosoft for trojan removal..free trial available: http://www.moosoft.com/products/cleaner/download/
i would do all in safe mode~~
always a great place to visit in addition to housecall