Half Life 2 Episode 2 Won't start

Hello, sorry if this is in the wrong section. Episode 2 and Episode 1 won’t run, it gets to the little “Preparing to launch” window, it says I’m playing for a couple seconds (the window just exits out) and then nothing. I’ve also verified and defragmented the cache. I even tried to uninstall Episode 2.

Also, I have a quick question about the Source SDK , cause I’m a noob at it. When I try to run it(Do I run Source SDK base 2006 or 2007?) I cannot load HL2 (or episodes) as a current game no matter what engine version I’m in. This seems like a pretty easy problem to solve, but I can’t seem to solve it. Please help.