Need help launching Half-Life 2: Episode One - SteamVR update required?

So here's the deal.

I bought HL2: EP1 and HL2: EP2 yesterday, downloaded them, and now when I try launching HL2: EP1, an error message appears, saying:

Failed to start game with shared content. Please update these games first:
SteamVR

Upon installing that SteamVR thing however, it still says the same thing.

1. I checked integrity.
2. I re-installed SteamVR.
3. Re-installing the whole game again is a last resort. My internet connection is too slow, it takes a whole night to download a medium-sized game.

SteamVR shouldn't usually be required to play HL2: EP1, as far as I know. And since the episodes are standalone, I shouldn't need to install any other crap to play it...
If anyone could help me with this issue, I'd appreciate it.