To backup a private key on Microsoft IIS 6.0 follow these instructions:

1. Open the MMC (Microsoft Management Console)
From your server, go to Start > Run and enter mmc in the text box. Click on the ‘OK’ button.

2. Add the certificate snapin
a. From the Microsoft Management Console (MMC) menu bar, select Console > Add/Remove Snap-in.

b. Click on the ‘Add’ button. Select ‘Certificates’ from the list of snap-ins and then click on the ‘Add’ button.

c. Select the Computer account option. Click on the ‘Next’ button.

d. Select the Local computer (the computer this console is running on) option. Click on the ‘Finish’ button.

e. Click on the ‘Close’ button on the snap-in list window. Click on the ‘OK’ button on the Add/Remove Snap-in window.

3. Backup the private key
a. Click on Certificates from the left pane.

b. Look for a folder called ‘REQUEST’ or ‘Certificate Enrollment Requests’ > Certificates

c. Select the private key that you wish to backup. Right click on the file and choose > All Tasks > Export…

d. The certificate export wizard will start, please click ‘Next’ to continue. In the next window select ‘Yes, export the private key’ and click ‘Next’.

e. Leave the default settings selected and click ‘Next’.

f. Set a password on the private key backup file and click ‘Next’.

g. Click on ‘Browse’ and select a location where you want to save the private key Backup file to and then click ‘Next’ to continue. By default the file will be saved with a .pfx extension.

h. Click ‘Finish’ to complete the export process

You will get a message that the export was successful. Please copy the backup file.