I downloaded CentOS 5 and put it on a machine (2.4ghz, 256mb, 128mb radeon 9500) as a server for my windows network to use at home. I'd like to be able to at least use it as a file server for within my house, and from over the internet if possible. I'm very advanced with using Windows, but I'm new to Linux and the "art" of creating servers. So far, I'm able to see my shared Windows folders from CentOS, but from my Windows machines, CentOS is virtually invisible. If anyone could help me set up my machine with CentOS 5 to be a server on a Windows network, I'd greatly appereciate it.

You'll need to install and configure SAMBA as part of your Windows workgroup or domain. You can just get the SAMBA packages via yum if they're not installed already. Editing the configuration file is really simple -- it's well commented and there are also guides up on the Web. There's also a GUI tool called SWAT which you can install and use for configuration.