Solution 1:

Try OpenVPN (http://openvpn.net/). It's cross-platform, completely free, extremely secure, and once configured it's extremely easy to deploy. I can't confirm whether it specifically targets x64, but the x86 build should work on the x64 architecture.

Edit: I should mention that OpenVPN won a "Bossie" in 2007 as the best Open Source VPN.

Also, OpenVPN 2.1 is Vista-ready on both x86 and x64.