Hey guys I have a failed HDD off of a 250CI and I was wondering if a HDD from the local HDD store will work? any advice would be helpful. I have googled the P/N and really don't get much help. Or does anyone have a good used one??

just make it's the same speed, that's pretty much it.

how do I determine speed? and it looks like there is different connections for different HDD

Its on the label of the HDD, it's either 5400 or 7200, most probably 7200, but i have never looked. I do know it's a SATA HDD though.

Is there anything encoded on the series harddrive`s that would make you have to order it from KMA? Can you replace both harddrives together with non-KMA harddrives? Have yall had good luck with that?

You bring up a good point Dev, the 500 has a dual HDD in a raid 0 config. from Wikipedia

RAID 0 (block-level striping without parity or mirroring) has no (or zero) redundancy. It provides improved performance and additional storage but no fault tolerance. Hence simple stripe sets are normally referred to as RAID 0. Any disk failure destroys the array.
So if one HDD dies, you have to order both,( only on 500)
But no, there is no info on the factory HDD, just stick a compatible speed one, and format.