Are you using Steam?
Are you using version 1.2.3 of ESF?
I think so.
Are you trying to run any ESF add-ons?
What game are you trying to install ESF into?
Are you behind a router or firewall?
Router, yes. ports are forwarded. Firewall, no.
Are all your drivers updated?
What in-game video mode are you using?
Whatever the default one is, 800 x 600.
If you have an error message, what is the exact error message?
Refer to screenie.