Virus Infections From Scanning Ext. Drive

Ok, so I'm scanning my external hard drive. I copied some files from another computer to it, and I know some files were infected. I hook up the drive to another computer and scan it using Norton 2010. It finds Trojan Vundo, 4 times on the external drive, and it says some registry keys were created by the trojan on my computer with Norton 2010. 

 

Why? Did the Trojan create those keys when I plugged the drive in? I didn't open the executables. Did the Trojans execute when Norton scanned them? Does Norton open the files and examine them? Why didn't Norton block them from creating the entries; I have to restart my computer to remove the entries. 

Message Edited by windowslive on 09-18-2009 07:40 PM