I have to use files located on the Windows 7 machine from my Windows XP machine. About half the time the connection across the network is flawless. The other half of the time, the Windows XP machine doesn't communicate with the 7 machine or says Not Responding. Then finally after a few seconds it starts to connect. What's causing this lag?

Firewall is the possible cause. How does it work if you disable firewall on the computers? Additionally, please let us know if Password Protected Sharing is enabled in Windows 7. If it is enabled, please let us know if you are using same username/password on both computers.Please remember to click Mark as Answer on the post that helps you, and to click Unmark as Answer if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.