I try to reinstall the system software, scince i just got a new hard drive put in 500GB. It will not let me reinstall the 7.50 update. I dont know what to do.
Did you download the complete system software file?
Ensure you Downloaded the correct file from Sony. Notice there are two, one for a system update and one for complete system. The file should be around 1.1GB
Make sure you have your file system on the USB drive set up as PS4 > Update > PS4UPDATE.PUP and that the spelling is exactly correct.
Make sure you are selecting option 7 on the list, the rest should be greyed out anyway.
If there are any error codes, post them here, they can tell you a lot about what is going on.