Private key

Q. How can I export and import my private keys from one machine to
another?

A. By default, private keys are stored in the requesting user's or
computer's certificate store. If you use multiple machines, you might
want your private key on multiple machines. To do so, perform these
steps:
1. Start the Microsoft Management Console (MMC) (Start, Run, MMC).
2. From the File menu, select Add/Remove Snap-in.
3. Select the Standalone tab and Click Add.
4. Select Certificates and click Add. Click Close.
5. Click OK to the main Add/Remove Snap-in dialog box.
6. Select Certificates, Current User, Personal, Certificates.
7. In the right pane, right-click the certificate you want to export
(e.g., Exchange User) and select All Tasks, Export, from the context
menu.
8. Click Next to the Export Wizard welcome dialog box.
9. Select "Yes, export the private key" and click Next.
10. Leave the default export options and click Next.
11. Enter a password for the export and click Next.
12. Enter a location and name for the exported key and click Next.
13. Click Finish in the summary dialog box.
14. Click OK to the export confirmation dialog box.

Copy the export key file to another machine and perform the following
steps to import the key:
1. Start the MMC console.
2. From the File menu, select the Add/Remove snap-in.
3. Select the Standalone tab and click Add.
4. Select Certificates and click Add, then click Close.
5. Click OK to the main Add/Remove Snap-in dialog box.
6. Select Certificates, Current User, Personal, Certificates.
7. Right-click Certificates and select Import from the context menu.
8. Click Next at the Import Wizard welcome screen.
9. Enter the name of the file to import, as Figure 18
(http://list.windowsitpro.com/t?ctl=1B162:24641 ) shows,
and click Next.
10. Enter the password for the export file and, optionally, select
the check box to enable the key to be exportable again in the future.
Click Next.
11. Select the option to store the certificate in the default
Personal store and click Next.
12. Click Finish to complete the import.
13. Click OK to the import confirmation message.
After the import is complete, encrypted messages will be readable on
the additional machine.