VPN connectivity error 800 in Windows 7

It means Your vpn client can't reach VPN server. Try pinging it to check if server is alive.
For more information on troubleshooting this error please refer to link:
http://technet.microsoft.com/en-us/library/cc772616%28WS.10%29.aspx#BKMK_1

Are you using a router/firewall device?
Is the (R)RAS server the same as the Internet Gateway?
Are you using PPTP for VPN connection, or have you setup something special?

I am using RAS server but Internet Gateway is different ..I can able connect to other users at different locations ..
 getting this error for a one particular laptop only ..

Temporarily disable Windows Firewall on that laptop, though it should not block the necessary ports and protocols.
Does it work from other laptops/machines using the same (!) internet provider? I'm talking about the client side, not the server side.

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Already disabled Windows F/W ,but doesn't works .. .
It works with other users ..but not at the same location ..
Adding the error  page to get some help
VPN-error.doc

Enable the logging, and try again. Than observe the logfile, or post it here. As I can see it is a L2TP/IPSec connection, which is pretty reliable usually.