Please try steps below to resolve the issue:
1. On the switch try decreasing the queue set value i.e. try changing the Queue set from 4 to Queue set 2, which is more buffer efficient with larger buffers.
1. Type enable
2. Type configure terminal
3. Type qos agent buffer maximum
4. Type qos agent oper-mode enable
5. Type qos agent oper-mode enable
6. Type qos agent queue-set 2
Note: "qos agent buffer maximum" allows for maximum amount of resource sharing
2. Disable auto-tuning on the Windows 7 machines
3. Check / change cables and review port stats on switch for FCS errors or any sign of potential hardware failure.