Upgrading HyperV from Beta to RC0 on HP Proliant servers
While upgrading my Hyper V from Beta to RC0 on my HP Proliant M115 server, it cronked out at 54% (somewhat) and refused to proceed any further. One bad mistake I made was not to properly shut down my VMs before patching the server (serves me right for not reading the instructions before applying the patch). So, Rule number 1 -> Read this article.
If you have a HP server, there's a reported bug with the HP network utility that interferes with the patch from Microsoft. Follow this article if the installer hangs at 54% and you cannot resume it after that.
Now that the host OS is patched successfully, go to Hyper V Manager and copy each VM's settings, and remove every one of them. Afterwhich, recreate the virtual machines, pointing to your existing .vhd files. Now, you'll need to patch each guest VM separately. Without this step, your guest VM will not have network connections.
Update for Windows Server 2008 x64 Edition (KB949219)
http://www.microsoft.com/downloads/details.aspx?FamilyId=DDD94DDA-9D31-4E6D-88A0-1939DE3E9898
Update for Windows Server 2008 (KB949219)
http://www.microsoft.com/downloads/details.aspx?FamilyId=B7464B44-821D-4A7C-9D9C-7D74EC14437C
To install the latest version of the Integration Services for Windows Server 2003, for Windows Vista SP1, and for Windows XP SP3, click Insert Integration Services Setup Disk on the Action menu in the Virtual Machine Connection dialog box.
Once you've updated your guest vm successfully, you'll need to pull up Device Manager and remove those devices showing error and remove them. Once all those problematic devices are removed, click on 'Scan for Hardware Changes' and your vm should have it's network connectivity back up.
That should be it! Have fun!