How do I set up a VPN connection to my Linksys WA54G ADSL router?

I want to set up my Linksys router so I can connect to it from outside the office as a VPN client and then access the office servers / etc. I am assuming i can use the default Win XP VPN connection to connect to it, but not getting very far.

What is a VPN?

VPN is (Virtual Private Network) were first used by companies to enable their employees to securely access internal systems such as email remotely (e.g. from home or while on business trips). Today they are increasingly being used for personal use by individuals to protect their privacy while online in public places (e.g. when using the wi-fi connection in a cafe) or in a country where the internet is censored / blocked (e.g. China, Saudi Arabia��).