Extreme lag

Alright this happened awhile ago but my Hammer keeps lagging horribly. I can go around my business for about a minute until this lag just hits me. I can use DoD:S, TF2, just fine, but every time I try and use CS:S and Half Life (All of them) It just happens. I have already refreshed my content, re-downloaded the SDK and all the obvious stuff. So is there anyway someone can give me an answer here? Also, my computer has run Hammer before fine.

I was having this problem a while back. It seemed to solved itself over time or it was from me updating my drives.

Well, I have tried waiting it out but no luck.