Ah, okay, you're running out of space on that drive because of the mdmp file. Do you have any of the following trace flags enabled?:
Trace Flag 2551: Produces a filtered memory dump
Trace Flag 2544: Produces a full memory dump
Trace Flag 2546: Dumps all threads for SQL Server in the dump file
You can check by running DBCC TRACESTATUS. A value of 1 in the Status column indicates that the trace flag is on, a 0 means that it is off.