Answer:

A keyboard from before the computer mass market

I have keys but no locks.

Keyboards have keys, but modern keyboards include Caps Lock. Early computers only had upper case letters, so there was no need for a caps lock.

I have space but no walls.

Spacebar

I have enter, but you can't leave.

The Enter key (sometimes called Return)

Answer:

A keyboard from before the computer mass market

I have keys but no locks.

Keyboards have keys, but modern keyboards include Caps Lock. Early computers only had upper case letters, so there was no need for a caps lock.

I have space but no walls.

Spacebar

You can enter, but you can't leave.

The Enter key (sometimes called Return)