WSUS or any free updating software

Hello,
I am currently looking into updating all my computers on my network from one software. BUT there is a catch. The software can NOT be on the server. Is it possible to install WSUS and be able to use it on a Windows XP computer to distribute windows updates to all my other computers in that way? Or will I have to install the server part of it on a regular server? Can I just install it on windows xp along with the client version? And if not, does anyone know a software who can let me choose to install different windows updates on a network at a certain time. In order to increase the productivity. Any help will be appreciated. Thank you. 🙂

Sincerely,

Alina