Engine Error: Could not load library client

[RocketRunner]

Explanation: Recently, I had to get a new computer because my old one won't start up anymore. I take the Obsidian Conflict folder from the backup I had made of my old one, and put it in the Source Mods folder. I reinstalled all of the games I'm certain I mounted on Steam, started them all up once, and when I went to play OC, it crashed immediately and spat up the error in the thread title.

I'm certain that this problem can be easily fixed and possibly not worthy of another thread, but the Wiki FAQ doesn't have the error I'm talking about listed there and I don't know how to fix this. Could it be that moving it from an old backup messed some stuff up? Should I reinstall? What else haven't I tried? (EDIT: It occurs to me now that I should try verifying the games in question.)

And I also apologize if this came up before, but searching for "Engine Error" only gives me that thread which had a different error.

EDIT: I should take this to Bugtracker.

[Neico]

that error says that a dependcy for the dlls is missing, this could be anything: tier1.dll engine.dll etc. maybe you should check your source sdk base 2007~

[RocketRunner]

There's a tier0.dll and a tier0_s.dll, but no tier1.dll.

Any other DLL files I should look for?

EDIT: To anyone who reads this and replies: I suspect that Windows Backup might have lost some files in the Backup process (but this seems to be on the end of the Source SDK '07 Base (which I reinstalled through Steam), as Neico just said up there), this problem is also posted in Bugtracker (by me, of course), and I'm considering a reinstall of the full mod since there is most likely no way I can get the DLL files back (unless I verify the SDK base, which I'm not sure I've done yet). If a Mod wants to, they can lock/delete this thread, but I'll leave it up for now in case some other person has this issue.

EDIT 2: Reinstalled. It looks like reinstalling fixed it.