Registry check

Yes I'm a newbie.  I'm a NIS user with my Windows Vista Basic OS.  During a web session Norton warned me that my registry may have been compromised.  The message included a description of Trojan Horse (TH) malware.  I attempted to execute a restore point (not sure if that's the correct term), but Windows told me it was unsuccessful.  I was told yesterday that someone attempted to use my Visa account number and I had to close the account.  This morning I used the on-line support tool from Norton which installed the most current version of NIS 2012.  My NIS is reporting System Status: Secure.

 

How can I be sure there is not a TH in my registry?  Thanks in advance for your help.