SNMP query for Windows Partition w/ no drive letter

I am trying to query a windows partition on our Exchange servers that doesnt use a drive letter.
I have walked the OID and can get a response
SNMP OK - “E:\Database\Archive” “E:\Database\TempStore” (the drive letter is actually a mount point here)
but I am having troubles using the -w -c variables …

./check_snmp -H ip_address of host -o, -C snmp_string_here -w 80:90 -c 90:90
No valid data returned
any help?

also tried
./check_snmp -H 10.x.x.x -o -C xxxxx -w 80 -c 90
No valid data returned