Files to review when troubleshooting VSS snapshot errors

To determine the cause of VSS errors on your system you can run the following commands on the windows system from a command prompt with elevated privileges (Run as Administrator) and review the content

For Windows 2003

C:\> vssadmin list writers > C:\temp\writers.txt
C:\> mountvol > C:\temp\mountvol.txt
C:\> vssadmin list shadows > C:\temp\shadows.txt
C:\> vssadmin list shadow-storage > C:\temp\shadowstorage.txt
C:\> vssadmin list providers > C:\temp\providers.txt

For Windows 2008 and 2008 R2

C:\> vssadmin list writers > c:\temp\writers.txt
C:\> vssadmin list providers > c:\temp\providers.txt
C:\> vssadmin list volumes > c:\temp\volumes.txt

C:\> diskshadow /L c:\temp\shadow.txt
DISKSHADOW> list writers detailed
DISKSHADOW> exit
C:\>

Reference: https://technet.microsoft.com/en-gb/library/cc772172.aspx