Backdoor.Tidserv - Power Erasure didn't erase!

Hi,

 

Help please!  Norton Internet Security found 2 x backdoor.tidserv files which needed to removed '''manually'.  I installed Norton Power Erasure and this located and got rid of 1 of the backdoor.tidserv files but the other one is still there and I've now run the 'power erasure' several times.

 

Any help greatly appreciated.

 

thanks

 

Nicola