HL2.exe Error

I have been having issues with GMod, Half-Life 2, and Counter-Strike:Source. I have been trying to resolve this problem for awhile now, but what I have tried so far didn’t work. Every time I open GMod or any other Steam game, I get the error message, “hl2.exe has stopped working” and it crashes. I typically do not even see the loading screen; however, I have been able to get there on a few occasions. I am running Windows Vista OS (32-bit).I have tried things such as -dxlevel and I get nothing.I have downloaded it four times.I have pasted the Problem Signature under the following message.

Problem signature
Problem Event Name:APPCRASH
Application Name:hl2.exe
Application Version:0.0.0.0
Application Timestamp:4c0de821
Fault Module Name:StackHash_7dc0
Fault Module Version:0.0.0.0
Fault Module Timestamp:00000000
Exception Code:c0000005
Exception Offset:01750000
OS Version:6.0.6002.2.2.0.768.3
Locale ID:1033
Additional Information 1:7dc0
Additional Information 2:b4ee5de6a2322745523997a782b35692
Additional Information 3:027b
Additional Information 4:277e19c30fbd5f6bb531ec9e027c37c3