Create New Firefox Profiles in Windows 7.

Step 1: 
Go to the Windows Start Menu and then select 'Run'

Step 2:
Enter firefox.exe -P
















Step 3 : Click on the 'Create Profile...' button on the 'Firefox - Choose User Profile' window.

Step 4: Click on 'Next >' in the 'Create Profile Wizard' window.

Step 5: Enter new profile name in text box  'Enter new profile name' box and click on 'Finish' button.

Step 6 : Click on Finish Button and Profile is Created.

Step 7 : Click on Start FireFox.

It will launch Firefox instance of newly created Profile & whatever the profile which is selected would be default opened Profile.