1451 - Warning: Unable to open file ... (The system cannot find the file specified)

Symptom

Thie following warning message is seen when a file is in use and therefore being handled by VSS (since VSS creates the GLOBALROOT snapshot path):

Warning: 21:48:35 Unable to open file: C:\Program Files\Computers\Diagnostics\
ServiceHost_20100620192402.xml, reason:\\?\GLOBALROOT\Device\HarddiskVolumeShadowCopy191\
Program Files\Computers\Diagnosticss\Diagnostics\ ServiceHost_20100620192402.xml 
(The system cannot find the file specified)

Cause

When you see this error, the problem is typically with VSS. It often indicates that the snapshot of the specified file is not available, as VSS will have overwritten it if there was insufficient space.

Solution

Increase the volume shadow copy area. The cause may also be another VSS error, so check the event logs for volsnap or Volume Shadow Copy errors.