TOPIC: Please can someone explain to me

So i was just browsing and see this old sack of shit being updated

There's a few things you can check.

1. Do you have another game running

2. Do you have something else installing.

If both answers are no, open Task manager and end the process of Steam, and retry.

Edit: I posted this before you edited the second line in. Chances are, it just had a small texture patch or something.

Engine update?

it's an update for an old game that hasn't been updated in years

This was actually updated today.

It could very easily be a security update.