Can't share with XP

I have a Windows 7 and XP computer on a router. I set up the network on both computer and map drives on both computers which I can see so My network in working but when I try and access the date on the other computer it give me something about not enough space which I have plenty of or don't have permission and I'm the administrator. Any ideas?

Please be more specific. Which computer is giving you trouble, the one running 7 or the one running XP? Exactly what's the message it gives you ("something about not enough space")? What don't you have permission for?

Off-hand, only thing I can think of is that (I think) you need to set up the Windows 7 computer to use only 40/56-bit encryption as the XP system can't use 128-bit encryption for networking.