You'll have to FTP into somehow (providing you didn't have a softmod and it got wiped), so start
here for networking. You'll at least need one CAT5 crossover cable to connect your XBOX to your computer NIC (network interface card).
Then, if your main dash (Evox, Avalaunch, whatever it was) is gone too, you'll need to make a bootdisc
in order to FTP in. You can try it the
manual way, or if you don't what the hell that's talking about, you're better off with a copy of
SlaYer's Evox Auto-Installer.
Then, if all your apps are truly gone (I doubt it, they're probably still there in your E: Drive if you still have the retail 8gig HD, or in F: Drive if you've got a larger drive installed), you'll have to go get them from
"the usual places" and install them again.