Low Disk Space Error for a drive that doesn't exist

I am running SBS 2003 and for the past couple of months, I get this error (see below) in my server performance log.  The problem is that there is no disk called "HarddiskVolume5) and all the actual drives are nowhere near full.  

One suggestion I tried was to run the disk check if this was related to bad sectors.  The disk check ran, but it did not affect this error message.  It does not appear every day, but frequently.  

Server is HP Xeon, 2GB Ram, 2 mirrored SATA HD (4 drives) - 160GB and 80GB.  

Any ideas?
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Low Disk Space (HarddiskVolume5) 8/3/2007 9:16 AM 1
The following disk is low on free disk space. Low levels of free disk space can cause performance problems and prevent users from saving files on the disk.

Drive Letter: HarddiskVolume5
Free Disk Space: 0.000000. MB
% Free Disk Space: 0.000000.%

You can disable this alert or change its threshold by using the Change Alert Notifications task in the Server Management Monitoring and Reporting taskpad.
  Low Disk Space (HarddiskVolume5) 8/3/2007 9:16 AM 1
The following disk is low on free disk space. Low levels of free disk space can cause performance problems and prevent users from saving files on the disk.

Drive Letter: HarddiskVolume5
Free Disk Space: 0.000000. MB
% Free Disk Space: 0.000000.%

You can disable this alert or change its threshold by using the Change Alert Notifications task in the Server Management Monitoring and Reporting taskpad.