What piece of networking equipment do I need?

[Beano]

OK, as far as i know - what you're asking for is not possible.

What you want:

Internet > Wireless router:

Then what you can do is you can use Ethernet cables , one for each PC - in to the router.

Otherwise, you want 4 different wireless dongles / PCI wireless cards - one for each PC.

It is possible. I've seen it done a few times before and I've read about it a couple of times but I can't remember where.

Hold on, let me find something...

I understand what you mean,
U want 4 computers to connect to the wireless router via 1 wireless adapter, I'm not sure if this is possible, you may have to buy seperate ones.

Yes! This is exactly what I mean! It is possible, I just can't remember what the specific piece of equipment is.