1) Insert the Window Installation CD - DISK 1. 

2) Login into your VPS using remote desktop (RDP)

3) Go to Start > Control Panel > Add or Remove Programs > Add/Remove Windows Components

4) Go to Application server > Internet Information Services (IIS) > Enabled File Transfer Protocol (FTP)

5) Click OK until finished.

6) Click Next to proceed with the installation.

7) That it you have just installed FTP service in IIS6 manually.