SMTP stands for simple mail transfer protocol. It is basically used for sending and receiving the mail, whereas, POP stands for post office protocol it is used for mail receiving purpose in the network.
You need to re-install another system, latest anti-virus software and an O.S with latest patches. Before you start your system, connect the infected HDD as a secondary drive then scan and clean the infected hard drive. Once done, you can copy the files into the system.