Sound, firewall/antivirus, host process, all not working

I have no working sound and reinstalling/uninstalling the drivers doesn't
work. In programs, sounds fail, mp3s and videos don't load at all, and in
games it says I have no audio device.

The taskbar lower right icon for internet shows no connection but I have a
connection (I'm on it now).

The Windows Host Process keeps crashing and brining up a window to that
effect.

The security center shows no antivirus and no firewall, but I'm running both
(PC-Cillin). It previously detected that I was running these.

The internet lags.

All these symptoms occured at once. I've found at least two other people
who started having identical problems with other programs (e.g. Norton
Antivirus instead of PC-Cillin) at the same approximate time I did (last
week).

Help?