I have a dx7000 also (a DX7016-180) and I had a known hdd crash, I seen it comming so I purchased a seagate ata66/100 160gb hdd and cloned it now mine boots but needs a system disk (misplaced original). when I cloned the hdd I made a new one but will not accept it.
If you want to swap hdd and see if yours will boot on my hdd and mine on yours, or if you can clone your drive that could work also, with a system disc.
I tried to get replacement hdd from Pelco but they want me to send unit in for repair.
I believe they'll charge w/shipping $800-$1000 to replace hdd for you and diagnose. If its a bad Motherboard it depends
The earlier motherboards w/810 chipset are no longer avail. and not supported. The 815 chipset are still supported by Intel but getting hard to find.