Garry's mod won't load.

Hiya people of Facepunch, I’m a new guy (well I downloaded Garys mod yesterday) and I downloaded the Tf2 and gary’s mod pack. But tf2 works fine but the garys mod won’t run. It gets to the screen where there is a guy with what appears to be 2 guns (one on shoulder and one at his side) with a little black box in the corner of the screen saying loading. after that the game closes and says hl2.exe. And I don’t know what to do?it says this:Problem Event Name: APPCRASH
Application Name: hl2.exe
Application Version: 0.0.0.0
Application Timestamp: 470c11ae
Fault Module Name: ntdll.dll
Fault Module Version: 6.0.6002.18005
Fault Module Timestamp: 49e03821
Exception Code: c0000005
Exception Offset: 0004a4d2
OS Version: 6.0.6002.2.2.0.768.3
Locale ID: 3081
Additional Information 1: bfef
Additional Information 2: e8adce1c2b9e7be834b4063ac3c53863
Additional Information 3: bfef
Additional Information 4: e8adce1c2b9e7be834b4063ac3c53863