DEP eh? Could be a conflicting program, or a trainer/ hack... Do you mod? if so, don't log into a LIVE account, make a local one and use that one instead with modded maps. THAT or your install is corrupted, once again H2V can does this so you need to see if again something is interfering with it.
You see DEP acts in H2V as an anti-cheat mechanism. So anything it sees as an attempt to cheat and it gets pissed off, sometimes crashing the whole thing.
If it's something graphical; as you've got quite a good rig, but seeing as H2V is a bad port,- It could be some minor setting, like the Resolution?
Have you run H2V as admin?
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