normally when system like a dell sits at the dell logo it probably is having issues either with a usb device plugged in or the hard drive
if you have usb thumb drives plugged in , remove them, leave only keyboard/mouse, do you see the F2/F12 keys information top right corner of the screen?
can you try to boot machine again (press power 5 -6 seconds to shut it down manually and try again) and as soon as logo shows press F2 and I am hoping yuou can jump into the bios, in there look for SATA information and see if the system is recognizing the hard drive.