Automating VPN connection

Hello,
I've been tasked with looking for a way our users can connect through VPN to our servers without actually going through the standard VPN login sequence with the native windows VPN software. Our remote users are using Windows Vista and Windows XP currently, I think a few of them have Windows 7 now. I know that Windows 7 has DirectAccess to do what we're wanting to do however, as a non-profit organization we're trying to keep from shelling out the money to upgrade all our computers to Windows 7. So my question is, are there any ways to do what DirectAccess does for Windows 7 (connect to VPN without the VPN login sequence that is) on a Vista or XP machine?

Edit: I forgot to mention that I have researched several different ways to do this, however I'm looking for a simplified way that doesn't require the IT department to send out people to each remote site and set them up manually. Thanks in advance for any help.

Kenneth,

DirectAccess really does sound like it is going to be your best bet. Have you checked out the Windows 7 ROI tool to see how much your company could save by moving to Windows 7? To use the Windows 7 ROI tool, please go here: roianalyst.alinean.com/msft/AutoLogin.do?d=893919303036409099

Jessica
Microsoft Windows Client Team