Open the Start menu, type "certmgr.msc" in the "Search programs and files" box and press "Enter." The Certificate Manager will open up.
Confirm the operation or re-type your password, if prompted. Open the "Personal" category in the left navigation pane, click on "Certificates" and then click to select the certificate that says your account name under the "Issued To" heading.
Open the "Action" menu, move your cursor over "All Tasks" and click the "Export" option. Follow the prompts in the export wizard. Select the "Yes, export the private key" and "Personal Information Exchange" options when prompted, type a password for the certificate and click "Finish" when done.
Transfer the certificate file to the computer you want to open the encrypted file on and open the Certificate Manager on that computer. Open the "Personal" category, open the "Action" menu, move your cursor over "All Tasks" and select the "Import" option.
Follow the prompts in the import wizard. Select the certificate file you transferred, type the certificate password, check the "Mark this key as exportable" checkbox and select the "Personal" category as the location for the certificate to be placed, when prompted. Click "Finish" when done. Double-click on the encrypted file to open it; the certificate you just transferred will grant you access to the file.