Can't find OIDs for physical drives - DL380 G4

[Saturnnights]

We have a lot of DL380 G4's running Server 2003.  We've recently installed PRTG and I want to have it monitor the state of our physical hard drives via SNMP.  I'm very new to SNMP and so I'm missing something here.  When I download the MIB files (I've tried quite a few now) that are supposed to have the OID's for this server, I get quite a few OID's for many devices, but nothing specific for the DL380's physical drives.  I've looked through all of the MIB's with a MIB browser and don't see any OID's clearly identified that would signal a drive failure. 

Interestingly, I have run Paessler's SNMP tester against a test server and found no mention at all of the drive slots or anything related.  If I yank out a drive, then re-run it, a new OID that identifies the drive failure is created and incremented with a number at the end that if I try this again, increments one number each time.  Those OID's are informational only and don't appear until I have an "event" like a failure.

I've been working on this for a few days and I'm very frustrated and have come to beleive that I'm doing something wrong - I just don't know what.  I have Dell servers that I can go right to Dell, download a MIB file specific for their service tag, then browse it and there are OID's clearly labeled throughout.  I plug them into PRTG and they just work.  Finding OIDs that will tell me when my DL380 has lost a drive has been a frustrating pursuit and I don't know where to look?

If I google this, I see zillions of references to just downloading the MIB file, but the MIB files that I find on HP's site are not very specific and are missing lots of OIDs.

Can anyone point me in the right direction?

Many thanks,
Mark