Vmware Virtual Machine running Windows 2008 R2 Server will not boot with error STOP c000021a

I migrated one of my Sharepoint Servers running in a vSphere 4.1 virtual machine, the migration went fine but when I came to start the guest I found it would not boot up, it booted to the Windows Recovery and then the recovery console could not repair the installation.

So I spent the next day literally going though every option in Windows Recovery Console, bcdedit and bootrec both helped get from a total non boot message of "bootmgt is missing" to a point where I could find my Windows installation again.

The next issue I had was that Windows would start to boot but it would hang on the green progress bar and black boot screen, I thought it may take some time so I left it for several hours and it made no difference.  So back into recovery console I used diskpart to look at the partitions and volumes and I could see that both my System Reserved and Boot partition were there but the System Reserved was set as hidden.

Using diskpart I changed this volume to not be hidden, this is volume 1 on a disk that runs Windows 2008 R2. I restarted the guest and now it would boot but then display an error "autochk program not found - skipping AUTOCHECK" this would then be followed with a BSOD with the error STOP c000021a.


Now this STOP error is you Google is usually a game ender but never one to quit I tried a search on Vmware knowledge base on this and hey presto I found this article.

http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=2004505


The answer is to use diskpart and make sure that the System Partition in Windows 2008 R2 does not have the value nodefaultdriveletter assigned to it.

So use the list volume command and if the volume has the value of true for nodefaultdriveletter then you need to change this as below

diskpart
list volume
select volume 1
attributes volume
attributes volume clear nodefaultdriveletter


I started the guest and it booted as normal!  This one change has saved me a Sharepoint rebuild and was worth the 12 hours of trouble shooting to learn to keep my ESXi servers up to date!