My VPN client (TheGreenbow) won't run under Vista, and I really didn't want
to drop $150 or so on the NPC client (which works very well, by the way).
As an interim fix, until TheGreenbow comes out with a Vista-compatible
client, I found that it runs fine in an XP Pro installation running under
VirtualPC 2007.

Microsoft is offering VirtualPC 2007 for free and it's a pretty slick piece
of programming. Once I installed XP Pro, I just installed TheGreenbow VPN
client as I would on any XP machine, configured it for my VPN router (a
consumer Linksys) and let it connect. It works fine.