First, thanks for your reply,

I did try yesterday to just to use natting but it didn't work, today I tried something, Stopped the firewall client on the client work station, and  opened the VPN connection using the ISA as gateway, It worked!!! 
But this way I lost control in the users and to what they acces on the internet?

I read the article posted in the isa.org about forcing VPN connection to pass thru the proxy firewall but it didn't work... I coulsn't open the http site after establishing the connection.

One more problem I worked around it, when I enabled the VPN thru ISA, which automatically turn on Routing and Remote Access service on the server; if I restart the server, the ISA firewall service will stop and not start? I checked the errors in the Event Viewer, the only thing I could get from the knowledge base is that it is about certificates, while I am not using certificates at all when using VPN or any other connection.
What I did is? i stoped the Routing and Remote Access Service, start firewall service, then start the routing and remote access again.

is there a better way to fix this problem also?

Thanks

George