I have a Windows 2003 server with a registered usage of 91%, but pulling up the process list from OpManager shows processes using only 6% of the available memory.

Is OpManager including file cache in its overall count, or is it counting total memory for the percentage different from how it calculates per process usage? 

The current warning I am seeing for example:

Memory Utilization is 87%, threshold value for this monitor is 80%: Top 3 Processes:-sqlservr.exe - 3%;Mcshield.exe - 2%;FrameworkService.exe - 1%