I have been evaluating 3CX Version 9 for a couple of weeks now and absolutely love it! This is my first 3CX install so please bear with me My setup is as follows: XEON E5520 with 8GB Ram Server 2008R2 running Hyper-V on LSI Raid 1 2 TB on dedicated LSI controller in Raid 10 (4 Sata 7200rpm drives) (2) Cisco SPA504G Phones as well as (2) 3CX Softphones All of my virtual machines are installed on the Raid 10 drives. My virtual machines are: -Domain Controller 1 GB Ram (Server 2008R2) Dedicated 10/100/1000 NIC -Exchange 2010 4 GB Ram (Server 2008R2) 10/100/1000 Dedicated NIC -3CX 2GB Ram 10/100/1000 Dedicated NIC When I try to run 3CX on a fresh 2008R2 Virtual machine the outgoing call quality, IVR and music on hold is fairly poor (i.e. clicking, popping and distorting). This is where the scenario gets strange: If I install 3CX on an existing Server 2003 Standard (2 GB 32-Bit version) Virtual using the same virtual switch as the 2008R2 machine and stored on the same Raid 10 setup the audio quality is great. No issues at all. Also, if I install 3CX directly on the Hyper-V host machine (Server 2008R2) the audio quality is excellent as well. So, this is what I've tried on the Virtual Server 2008R2 machine: -Changing the properties of the Virtual and Physical NIC (i.e. IPv4 offloading, buffers, etc...) -Changing to a different virtual switch -Implemented QoS on the Server 2008R2 virtual -Moved the virtual machine to a separate drive with a fixed VHD -Changed audio codecs, even tried using K-Lite codecs -Tried assigning 2 processors to the Server 2008R2 virtual instead of 1 -Shut down Exchange 2010 and increased memory allocation to the 3CX virtual (4 GB) -Desktop experience and Quality Audio Video is installed -Changed the heartbeat, time syncronization properties of integrated services -Checked and double checked the firewall settings using the firewall checker -Used Wireshark to capture and analyze SIP and RTP packets (nothing out of the normal showed up) On a side note; if I install 3CX on an existing Windows 7 virtual machine using the same virtual switch (virtual NIC) the audio is terrible as well. So, why is the audio quality so superb while running on the Server 2003 virtual machine as opposed to the Server 2008R2 and Windows 7 virtual machines, especially considering they all use the same virtual switch (not all at the same time though)? This would lead me to believe that the problem is not with networking. Any help/thoughts would be truly appreciated. While I don't mind running 3CX on the Virtual Server 2003 machine, I would much rather have it running on a current OS (i.e.Server 2008R2). Thanks everyone!