When I start the game hl2.exe , the valve screen apears , then the menu screen, in theat moment the game crash and a error screen apears ! it says saomething about LOW memory ! the PC has 4Gb DDR2 800+ A-Data ! The game works on XP 32 , is the same DVD ! sorry for my english ( I'm from S-E Europe)
Never heard of A-Data tbh.
What info does CPU-Z give on the DIMMS?
Try to boot with one stick at a time to check for bad modules.
Also, ctrl+alt+del and check out what background processes are running. If this is a pre-built PC then you may have a lot of bloatware - unnecessary software taking up valuable Memory.
As a final though, check your page file settings and make sure it is active.
Go to your Steam- My Games, right click Half-Life 2, go down to properties.
Click on 'Set Launch Options'.
Put "-32bit" in the box (without the speech marks), hit okay/apply and then run the game.
Hopefuly that should fix the issue, I had some trouble getting the game to run natively in 64bit mode, unfortunately this seems to be down to a recent patch that valve released.. seemed to break it for me anyway.