I'm not sure whether the problem is on my computer, or whether Steam's gone
to Mars at the moment, but - I normally play HL2 (single player) in offline
mode. I set it up for offline because when I purchased it, I was on dial-up.
A few months ago, I got DSL, and now find that even though the game is
configured to allow offline, the only way to actually play offline is to
switch off my connection before I start the game (which is a PIA).

So my first question (which I suspect the answer to is no), is as to whether
there's any way to start up offline without turning off my modem.

Secondary, and more important issue:

Last night, the game was running fine both on and off line (I started it
once with the modem off, it went into offline; later started it again,
having forgotten to turn off modem, it started up online but ran).

I'm trying to continue my game today, but when I try to start offline (e.g.
with the modem switched off), it tells me it can't start up because the
account information isn't on the local computer.
When I try to start online, it asks me for my password (which it shouldn't,
since it's been stored since August of last year), then won't connect. It's
given me a variety of error messages, including saying there is no account
by that name, then that Steam is having trouble connecting to the servers.

At any rate, I'm wondering if anyone can point me to where the password
should be stored locally, and how to edit it so that I can at least get
started up offline...