How to back up only one computer on a network to Time Capsule?

Please can anyone help? I have a Time Capsule set up on bridge mode (we are using a different wireless router to assign ISP addresses) as part of a local network of 5 computers. I only want the Time Capsule to back up one of those computers but it is currently backing up everything in sight and I cannot work out how to stop this! All of sudden 1TB is looking rather small.

When I open Time Machine and click "options" I can see other people's computers coming up as shared drives and can even see the general types of files/programmes etc that are on them but the "exclude" button does not light up to let me exclude these computers from being backed up.

Help, please!

The Time Capsule does not run backups on it's own.

You have to use Time Machine on each computer to back them up individually. Your Time Machine app is only backing up your individual computer.

If you're talking about the 'Shared' section of your sidebar in Finder, each item there is a separate, individual item including your TC. You are seeing each individual machine that is on the network that has sharing enabled. You can't select them in the Add to excluded list, because they're not being backed up by your Time Machine. You can see them, because it is opening a Finder window.

If you want to know what is on your TC, you need to open Finder and select/highlight it.

Thankyou, I'll have a look.

I was worried because my computer has 61GB of data on it but TC had filled up almost 150GB of space in just 2 days! If it is only backing up my computer (the others are PCs and definitely don't have Time Machine on them) why is a 61GB computer taking up so much space on the external hard drive?

Ironically I can't take a look at what is being stored in my TC because it is currently doing yet another back up of another 57GB of data?!!!

No, after the first initial backup, it only backs up the changes made since the last backup.

Can't answer what else may be on the TC. If you've only had it for two days and only have 61GB used space on your internal drive, 150GB used on the TC should not be from the TM backup only.

Hmmm. I've stopped the backup and had a look on the TC and I have definitely got some of my neighbours files on there! I can get into their music collection. Didn't go any further as obviously I don't think it is appropriate.

Help! They've got PCs. They definitely haven't got Time Machine on their computers.

If it helps our set up is a local network via a Belkin wireless router that is connected to a TC via an ethernet cable. The TC is set to bridge mode. I've ticked file sharing (as I can't do any backups if it isn't). My Mac connects to the internet via the signal sent out by the TC.

I've done a bit more digging around and opened airport then clicked on the TC. Then I clicked on Discs and clicked again on my TC. There is says
Capacity: 929.5 GB
Available 786.5 GB
Used 143 GB
USERS 3

Which does seem to indicate that there are more people uploading data onto the TC than just my computer. I'm sure no one else is trying to use the TC and as I've said before none of the other computers have got Time Machine on them. Has anyone any idea what is happening and how I stop it? For now I've got Time Machine turned off.

Edited to add both the networks are password protected.