Virtual Private Network(VPN) allows you to create a protected/encrypted network between two machines using a tunnel, so other machines are not able to access this network. The VPN is created by one machine running a VPN client that connects to the other machine that is running a VPN server (RRAS).

For Win2k :

• Enabling VPN in RRAS Causes Connection Issues to Remote Networks (MS KB243374)
• HOW TO: Install and Configure a Virtual Private Network Server (MS KB308208)
• HOW TO: Allow Remote Users to Access Your Network in Windows 2000 (MS KB300434)
• HOW TO: Provide Secure Point-to-Point Communications Across the Internet in Windows 2000 (MS KB301194)
• Increasing Security on Windows 2000 VPN Server (MS KB255784)
• HOW TO: Configure Win2000 Pro to Win2000 Pro VPN Connections (MS KB257333)
• HOW TO: Connect to the Internet after connecting to a VPN Server (MS KB317025)

For WinXP :

• HOW TO: Configure a Connection to a Virtual Private Network in Windows XP (MS KB314076)
• Basic L2TP/IPSec Troubleshooting in Windows XP (MS KB314831)

For Win2k3 :

• HOW TO: Allow Remote Users to Access Your Network in Windows Server 2003 (MS KB323381)
• HOW TO: Install and Configure a Virtual Private Network Server in Windows Server 2003 (MS KB323441)
• HOW TO: Provide Secure Point-to-Point Communications Across a Internet in Windows 2003 (MS KB324747)

More Info MS KB241252

Related Microsoft L2TP/IPSec VPN Client