-2) Realize that you don't understand anything about Vulnerability Assessment or Penetration Testing methodology(ies). Take some training.
-1) Realize that you're probably going to break something and cause problems for yourself, a business, other people.
0) Since its your machine or a machine you have written/documented permission to test you obviously know if it's NT or not..... Or you have sufficient skills to otherwise deduct the OS type and perhaps version.
1) Check if the vulnerability exists (Nessus? OpenVAS? SCUBA? etc).
2) Read up about the vulnerability (Secunia, Mitre, etc)
3) Find a exploit for the vulnerability (Metasploit?)
4) Read up on how to use Metasploit (or whatever).
5) Configure Metasploit (or whatever) and run the exploit.