file sharing on home network

I have file sharing set up between two computers running xp on my network. If one computer is turned off, you cannot access the shared files on that computer. Makes sense. What I'm wondering is, is it possible to have a central location where files can be stored so you don't have to worry about the computers being turned on? I'm unsure of how a setup like this would work. I don't want to spend the money on a server or anything. Does anyone know how this could be accomplished?

Will getting an external usb harddrive solve your problem?

Network Attached Storage Is probably what you are looking for. If you don't have the dough. Then another option is to find an older computer, and just through some HDD's in it then use install something like. FreeNAS Which will turn the computer into an inexpensive NAS. Well inexpensive besides the HDD's. This is what i use to store all my Media Center Recordings, currenly got 10 TB's of storage.