HL 2 memory crash

Hello,few days ago i downloaded HL2 from internet because i was bored so i wanted to play some older games.I normally start the game then i get message
Node graph out of sync and game starts to lagg and in few seconds the game will crash with this message

The Instruction at "0x00000000" referenced memory at "0x00000000". This memory could not be "read".

Click OK to terminate this program.

My computer is:
Pentium 4 3,20ghz
2gb RAM
Intel(R) 82945G Express Chipset Family 128mb

On internet i have read some fixes:
I have tried mat_dxlevel 71
Then i have tried adding +mat_forcehardwaresync 0 +snd_async_prefetch_priority 1 at game target
another problem is that the game is not installed i just downloaded it zipped and i start game with launcher and i also have this game on nonsteam

is there any fix or should i buy better Graphics card or buy that game from steam?

hope someone will be able to help me , thx