Primary hard drive not found and secondary

I,m new to the computer world but the guy at best buy said i would be able to install my a cd player on my own when i was finish the the computer screen was blue with an error message that had alot of numbers that i dont know anything about so then i restarted the computer now it says primary hard disk along with the secondary hard disk not found

 

Probably unplugged the ide cable (the flat ribbon cable that is likely gray in color) from the motherboard. Check to make sure your cables are plugged in and secure and try agian.

 

Thank you for your reply tollhouse frank,I think my computer is just too old it tells me to press f1 when i do that it just repeats press f1 this may sound kind of dumb but on the grey ribbon it says hdd1 and hdd2 can i put the drive on the #2 slot oh like i said the computer is old it's a 99 i gave to my son so i bought a new drive for him the computer is a dell and the hdd is maxtor do i have to get a dell drive