Hyper-V logs a lot of useful information if you need to diagnose a problem, so I thought I would put together a little post explaining where you should be looking.  The first thing to know is that all Hyper-V event logs are stored in the Event Viewer under "Applications and Services Logs", "Microsoft", "Windows":

There are then 10 categories for you to look at:

• Hyper-V-Config:
  This section is for anything that relates to virtual machine configuration files.  If you have a missing or corrupt virtual machine configuration file - there will be entries here that tell you all about it.
• Hyper-V-High-Availability:
  This section tells you about actions and changes that happen because of Hyper-V clustering.
• Hyper-V-Hypervisor:
  This section is used for hypervisor specific events.  You will usually only need to look here if the hypervisor fails to start - then you can get detailed information here.
• Hyper-V-Image-Management-Service:
  This section is used by the image management service to log information about virtual hard disk operations - like creating, converting and editing virtual hard disks.  If you have problems creating or editing a virtual hard disk - look here.
• Hyper-V-Integration:
  This section is used to log events that relate specifically to integration services.
• Hyper-V-Network:
  This section is used for events relating to virtual networks.  You will see information about the creation and configuration of virtual networks here (as opposed to virtual network adapters).
• Hyper-V-SynthNic:
  This is the section where information about virtual network adapters.  You will see entries in here each time a virtual machine with virtual network adapters powers up.  You will also see entries here if a virtual machine fails to power on because of a configuration issue with its network adapters.
• Hyper-V-SynthStor:
  This section is to do with virtual hard disks that are associated with running virtual machines (it is the storage equivalent of the SynthNic section).
• Hyper-V-VMMS:
  This section is where the virtual machine management services files its events.
• Hyper-V-Worker:
  This section is used by the worker process that is used for the actual running of the virtual machine.

Now - two pointers to keep in mind while looking at the Hyper-V event logs:

• If you do not know where to start, start with Hyper-V-VMMS.  As the central management service it usually has something to say about everything.
• Learn to follow the trail of event logs.  If a virtual machine fails to start because of a storage issue there will usually be events logged in the VMMS, Worker and SynthStor sections - and reading all of the events can usually provide better insight into the problem than just reading some of them.

Cheers,
Ben