disable this:
speed issues hyper v virtual machine vm server 2010 sbs 2011
http://serverfault.com/questions/504429/extremely-slow-file-transfers-to-hyper-v-vm-on-local-machine
also check drivers and
What's the NIC chip on the Hyper-V machine? If it's cheap/crappy (eg Marvell, Realtek, nVidia) there's your problem. If it's something good (eg Intel, Broadcom, QLogic, Emulex, Mellanox, Netxen, etc) have you followed the manufacturer's recommendations for Hyper-V (eg disabling: TCP Offloading, TCP Chimney, Large Send Offload, etc - these are the most common culprits, follow directions if they're provided). Also, are you running the most recent firmware (motherboard, NIC, etc)?
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