ok i have a Seagate Barracuda 250GB HP Model VB0250EAVER (ST3250318AS) SATA Hard Drive and i need to the max of hard drive i can run or allow on my DEll Optiplex 740 small factor tower plus also need help about if i can upgrade my ADM Athlon Dual core Processor 4850e and higher?
Any 3.5" drive at 2T or under should work fine. Upgrading the CPU would mean buying used - these CPUs went out of production not long after your system was current - and that was a decade ago.
so if i were to buy another sata hard drive and i wanted to upgraded, what would i'm looking for?
You'll need a standard 3.5" SATA drive - there are just three manufacturers left: Western Digital (which owns HGST), Toshiba, and Seagate (which also owns Samsung).
Choose from those three.
Unless you use a DELL hard drive you will get an Error.
"HDD replacement is not valid, continued use may result in long term HDD reliability issues, please press F1 if you would like to continue, and/or call Dell for replacement HDD" the replacement drive must be a Western Digital or Samsung because of thermal constraints in the chassis.