This thread was a great find, and so I wanted to add what I could in hopes someone else can benefit. I recently purchased used a DM/DS2AD/600/16. Mobo is a M2IPC2. It was running version 4.5(021) and M2IP 03.1(09.2). Got it for next to nothing and as expected, it wasn't working 100%. A software upgrade to 4.5(064) fixed everything, but I was suspecting the HD's were flakey. Original HD's were Hitachi HDT725032VLAT80's. Following the instructions earlier in this thread, I sucessfully upgraded the unit to two 500GB drives. New drives are Seagate Barracuda 7200.12 ST3500413AS SATA drives with Manhattan model 158282 SATA 300 to IDE converters on them (microcenter.com). I used Fat32formatter to format the drives (only needed to do a quick format), and Snapshot.exe to back up the original master HD to my PC and restore it back onto the new master HD per the directions. Both of the new hard drives with the SATA to IDE converters attached fit with the existing HD mounting brackets without a problem (this was a big concern at first - didn't want to re-drill the mounting plates for more space between the drives). Some notes on my experience doing this: This DVR has a RS232 port on the back, and throughout the process I kept a serial cable and terminal program running so the boot (debug?) processes could be monitored. This box defaults to 38.4k Baud. The initial software upgrade from CD didn't take, and this was readily apparent from watching the boot processes. Repeated it, and no errors. Lesson here was to watch it. I used Procomm Plus, which has a 1500 line scroll buffer. Wouldn't be a bad idea to have this written to a file for later review as 1500 lines filled up quickly. I intially tried using a pair of Western Digital Blue IDE 320GB 8MB cache drives (WD was the only brand 320Gb 8Mb cache IDE drive I could readily get), but no matter what I did, the unit didn't see them. Zip, nada, nothing. Must be something about the DM bios not playing nicely with WD. Watching the boot processes confirmed the unit was ignoring the drives. The Seagate SATAs installed with no problems at all. Please note that the Seagates have 16MB cache. Not sure if the SATA-IDE converter has anything to do with it, but a 8MB cache isn't necessary. After the Seagate drives were installed and running, the unit only reported 792GB of storage (200+GB for the OS? - I don't think so!). The upgrade-from-CD process was performed again, and the "Format all drives" option selected. Unit now reports 928GB of storage (much better). Have an upgrade CD handy before doing this. I also copied all of the most current software files available for this model onto a CD to have everything in one place locally if I needed it. Running Snapshot takes several hours. I was using an IDE to USB converter on the DVR hard drive, backing it up to an external USB hard drive. This was both to take a snapshot of the HD and then again to restore it. No problem though, set it and come back later was the rule here. I tried to copy the files directly without having to use Snapshot, but a couple of the files wouldn't copy for some reason. Blame Windows. StarTech SATA to IDE converters are used earlier in this thread, but I used the Manhattans because I could get them locally. I think any converter that will support drives over 137GB should work.