Try adding " -3dfxgamma" to your shortcut command line.

This is just a suggestion, and I'd be grateful for feedback from anybody with
more recent knowledge than mine as to whether it still works.  IIRC it used to,
even on non-3dfx cards, but I haven't played HL in a long time so I'm not at all
sure.  Can't do any harm though.

Alternatively, here's HQH's FAQ (though it's old, and not for the current HL
version):

============
Darkness

If the video settings are too dark and you can't see anything, then you can try
and up the brightness on your monitor's settings. If that doesn't help, then try
these two commands in the console:
gamma #
brightness #
Where # is any number from 0 through whatever. 0 = dark, 5 = 5x brighter, etc...
Do not try very large digits until you tried lower values and still stays dark.

When you give new values, you must reload the map Half-Life is on. I would
suggest you to load up an empty LAN server, choose any map, bring down the
console, type the following:

gamma 10

brightness 10

restart

Of course, if current values do not work, increment the values for the
variables.

If you have a 3dfx video card and Half-Life v1.0.1.0 or higher, then there's a
parameter that will let you setup how gamma is set up from your video card
properties found when right click on desktop. The parameter to be used with
Half-Life is: -3dfxgamma. Example: hl.exe -3dfxgamma

============
--
Paul

Thx for your replies guys, I shall give them a go.

Cheers

just wack gamma & brightness to 700 or 900 then put config readonly and yes
it still helps!

Ignore those fools, get some nice ray-bans....darken the screen and look
cool at the same time! =pp