Yes, you should be able to see your drives and files from each os.
In Windows Explorer in the XP Mode virtual machine, under My Computer, you should see:
3 1/2 Floppy (A) -if you have a floppy drive. Most likely not.
C on YourMachineName
Do you not see C on YourMachineName? It should appear and have the files that are on your physical machine's C drive.
In the Settings for your XP Mode virtual machine, change the Networking setting from Shared Networking (NAT) to the entry for your physical network adapter. This makes your virtual machine just like any other machine on your network. The same rules of networking and file sharing apply to virtual machines as physical machines. You can map a drive or create a share.