I was having a problem where Half-Life 2 was re-validating its files almost every time I tried to run it. I know other people have been experiencing this as well.
This is a pretty simple solution, but it worked for me. If you've been having the same problem, hopefully it will work for you.
All you need to do is make sure you right-click on the Steam system tray icon and exit Steam properly BEFORE you shut down your computer. The re-validation problem seems to occur after Steam hasn't been shut down properly and you have had to select "end task" in order to close it.
If this turns out to be useful for other people, perhaps it should be stickied.
This is a pretty simple solution, but it worked for me. If you've been having the same problem, hopefully it will work for you.
All you need to do is make sure you right-click on the Steam system tray icon and exit Steam properly BEFORE you shut down your computer. The re-validation problem seems to occur after Steam hasn't been shut down properly and you have had to select "end task" in order to close it.
If this turns out to be useful for other people, perhaps it should be stickied.