DHCP not binding to physical connection

Few days back i installed ISA Server on my windows 2003 server, when i
installed it all services to network was stopped. i started all services but
the DHCP is not running, Even though i uninstalled the ISA server now also it
is not binding to the physical connection.

when i boot the machine it gives a error that one or more service or driver
failed to load.

many times i uninstalled & installed the DHCP service but it is not working.

for the first time when i uninstalled the DHCP and installed it again it
worked and again when i restarted the machine it stopped working.

The main problem for that problem is the DHCP server is not binding to the
Physical connection.

Plz help me out



Bilal