PC to PC File Txfer extremely slow

How can I improve the LAN file transfer rate? Transfering files from PC to PC on my LAN is very very slow. This between 2 PCs through a wired 4 port Linksys BEFSX41 router. Transfering from shared folder on a PC to another shared folder on a PC. I can see the harddrive access is very infrequent and CPU utilization is very low. The network utilization shown under windows task manager is less then 5%. Download files off the internet is faster then the PC to PC transfer. There are no limits invoked in the router. Any tips appreciated.