Check out this nice list I found wondering on TechNet.
Mandatory reference in all Hyper-V implementation.
| Knowledge Base Article | Name | Date | Required? | Availability | Link |
| KB950050 | ”Hyper-V Update for Windows Server 2008 x64 Edition” (This is the RTM version of Hyper-V.) | 6/26/2008 | Yes. | Windows Update, Download Center | http://go.microsoft.com/fwlink/?LinkId=139066 |
| KB950182 | “A computer that is running an x86-based version of Windows Server 2008 or an x86-based version of Windows Vista may use fewer processors than expected if the number of cores on a socket is not a power of 2” | 04/11/2008 | Yes, if you want to start an x86-based virtual machine running Windows Server 2008 on a computer that uses a 6-core processor. | Hotfix | http://go.microsoft.com/fwlink/?LinkId=139067 |
| KB951308 | “Increased functionality and virtual machine control in the Windows Server 2008 Failover Cluster Management console for the Hyper-V role” | 09/11/2008 | Yes, for Failover Clustering. | Download Center | http://go.microsoft.com/fwlink/?LinkID=125397 |
| KB951636 | “Hyper-V Language Pack Update for Windows Server 2008” | 6/26/2008 | Yes, if you are using the additional languages offered. | Download Center | http://go.microsoft.com/fwlink/?LinkId=139069 |
| KB952627 | “Description of the Windows Vista Service Pack 1 Management Tools update for the release version of Hyper-V” (Install this to enable remote management of a computer running Windows Server 2008 with the Hyper-V role installed.) | 6/26/2008 | Yes, to enable remote management using the Hyper-V Manager Microsoft Management Console (MMC) snap-in. | Download Center | http://go.microsoft.com/fwlink/?LinkID=122189 |
| KB953585 | “Error message when you try to start a Hyper-V virtual machine on a Windows Server 2008-based or Windows Vista-based computer that uses the NUMA architecture: "An error occurred while attempting to change the state of virtual machine VMNAME"” | 09/04/2008 | Yes, if you are using a computer running Windows Server 2008 with Non-Uniform Memory Access (NUMA) architecture. | Hotfix | http://go.microsoft.com/fwlink/?LinkId=139068 |
| KB953828 | “The NLB host does not converge as expected on Windows Server 2008 Hyper-V virtual machines” | 6/25/2008 | Yes, if you are using Network Load Balancing (NLB). | Hotfix | http://go.microsoft.com/fwlink/?LinkId=139070 |
| KB956386 | “Microsoft Hyper-V Server 2008” | 10/03/2008 | No. | Download Center | http://go.microsoft.com/fwlink/?LinkId=139610 |
| KB956589 | “Hyper-V Update for Windows Server 2008 x64 Edition” (Install this to resolve potential issues when you manage Hyper-V with System Center Virtual Machine Manager (VMM) 2008.) | 9/23/2008 | Yes, if you are using System Center VMM 2008 to manage your environment. | Download Center | http://go.microsoft.com/fwlink/?LinkId=139611 |
| KB956697 | “Update for Windows Server 2008 x64 Edition” (Install this to resolve an issue in which the Hyper-V Volume Shadow Copy Service (VSS) does not back up virtual machines properly.) | 09/08/2008 | Yes, if the Volume Shadow Copy Service (VSS) is utilized for backups. | Windows Update, Download Center | http://go.microsoft.com/fwlink/?LinkId=139612 |
| KB956710 | “Update for Windows Server 2008 x64 Edition” (Install this to enable the Hyper-V role to support up to 24 logical processors and 192 virtual machines.) | 9/23/08 | Yes, if the management operating system has more than 16 logical processors. | Download Center | http://go.microsoft.com/fwlink/?LinkId=139613 |
| KB956774 | “Update for Windows Server 2008 x64 Edition” (Install this to resolve the scenario where a Background Intelligent Transfer Service (BITS) client cannot handle files that have paths that contain the volume GUID in Windows Server 2008.) | 9/23/08 | Yes, if GUIDs are used instead of a drive letter or mount point. | Hotfix | http://go.microsoft.com/fwlink/?LinkId=139614 |
| KB957967 | “Stop error message on a Windows Server 2008-based computer that has the Hyper-V role installed: "STOP 0x0000001A"” | 10/08/2008 | Yes. | Hotfix | http://go.microsoft.com/fwlink/?LinkId=139615 |
| KB958065 | “You cannot configure a Hyper-V virtual machine by using Windows Server 2008 Failover Clustering when the virtual machine uses a storage device that is managed by a third-party clustered file system or a third-party replication solution” | 11/03/2008 | Yes, if you are using a non-Microsoft clustered file system or non-Microsoft replication solutions. | Hotfix | http://go.microsoft.com/fwlink/?LinkId=139616 |
| KB958184 | “Virtual machine backup operations fail in Windows Server 2008 when Hyper-V virtual machine files are saved on a volume that is mounted on a failover cluster by using a volume GUID” | 11/05/2008 | Yes, when backing up a volume that is mounted using a volume GUID. | Hotfix | http://go.microsoft.com/fwlink/?LinkID=133348 |
| KB960578 | “The IRET and IRETD instructions do not support the Nested Task (NT) flag in protected mode in a Windows Server 2008 Hyper-V environment” | 12/17/2008 | Yes, if you have a program that uses the IRET (interrupt return) or IRETD (interrupt return double) instruction. | Hotfix | http://go.microsoft.com/fwlink/?LinkId=145170 |
| KB959962 | “An update is available for Windows Server 2008-based computers to address issues with backing up and restoring Hyper-V virtual machines” | 1/16/2009 | Yes, when backing up virtual machines. | Hotfix | http://go.microsoft.com/fwlink/?LinkId=145171 |