Microsoft Windows XP SP2

The following instructions apply to Windows XP SP2, whereas I assume all these rules also apply to XP SP1, XP and Windows 2000.

1. Go to network connections
2. Create a new network connection
3. Choose 'connect to the network at my workplace'
4. Choose VPN connection
5. Enter Company name
6. Choose to dial an initiating connection, if you have dial-up
7. Enter IP or hostname for your VPN Box
8. Finish

One might want to go to connection properties, networking tab and select L2TP IPsec VPN in the drop-down box (This speeds up your first connection try). Next step is to import the generated .p12 certificates on every windows-machine.

1. Open an mmc: Start | Run | type mmc | hit ENTER
2. Click File | Add/Remove Snap-in
3. Click Add
4. Select Certificates and click Add
5. Select Computer Account^2.5, click Next
6. Click Finish
7. Click Close
8. Click OK
9. Double Click Certificates
10. Right Click Personal, select All Tasks and click Import
11. Click Next
12. Enter the path to the .p12 file
13. Click Next
14. We stripped the password, so just click Next
15. Select 'Automatically select the certificate store based on the type of certificate', click Next
16. Click Finish

Done. No need to associate the Certificate with the Connection, as this is done automatically by Windows. In my project I automated this task, so that the clients would only get a setup.exe, the certificates would be downloaded from a secure server during the setup, and all other clickety stuff is done auto-magically (I used the Nullsoft installer and the Windows Scripting-Program Automateit for that).