Hi Sunny,
You have installed sap log-on pad which is, as suggested by Jude, intended for End users. you can not add or delete system entries in that.
You can install the correct software knowing its GUI and not Log-on pad or you can edit your saplogon.ini file to add or delete system entries in your Log-on pad.
you can find the saplogon.ini in C:\Users\<your logon name>\AppData\Roaming\SAP\Common for Windows 7.
AC