ISA and Outlook Express

I have installed ISA in integrated mode in win2k server. There are two problems coming to it :

1) The Outlook Express is not running on client machine. Not even any other Mail Client

2) The internet is being shared by clients perfectly but there is no browsing in the server machine where ISa itself is installed (Funny isn’t it?)

Though because I had to run that network so I had to rely on Winproxy to get the clients going with browsing and mailing but I really wana install and work with ISA2000.

Also I wana install Exchange2000 in the domain but I need to know all the precautions required if it is to share it’s work with ISA2000.

Please Help ????