I purchased a laptop for my sister and she backed up her old information to an external hard drive. She uses NIS 2011 as I do. She set up her Norton account to the new laptop and ran the initial scan and everything is clean and running just fine. When she plugged the external hard drive into the new laptop to retrieve files she received a Norton alert with "W32.tilleuvz!gen18" and it completely blocked the external drive. We are not getting any options to fix this threat ro scan the drive to repair this.
We would appreciate some information as to how to fix this virus so that the files can be accessed. I just searched the Norton virus and risks data base and this is not listed. 
Thank you