1. Connect the mobile device to the computer.
2. On the computer, start ActiveSync 4.1, and then click Explore.
3. Copy the root certificate file (.cer) to the device.
4. On the device, run the .cer file that is associated with the built-in Certinst.exe file.
If the security policy on the Windows Mobile-based device prevents the built-in certificate installer from working, try the following steps to install the certificate:
1. Download the SmartPhoneAddcert.exe tool to your computer. The following file is available for download from the Microsoft Download Center:Download the SmartPhoneAddCert.exe package now.
2. Run SmartPhoneAddCert.exe to extract the contents to a folder on your computer.
3. Copy SmartPhoneAddCert.exe to your device.
4. On your device, create a folder that is named "Storage." SmartPhonePAddCert.exe searches for the certificate in this folder.
5. Copy the root certificate (.cer file) to the Storage folder on your device.
6. Run SmartPhoneAddCert.exe. Click to select the .cer file that you copied to the Storage folder, and then install the root certificate.
資料來源 : 微軟知識庫文件 KB915840