Dell computer won't boot past logo screen, only loads half way

So I was trying to kill viruses on my Dell computer and I deleted some useless files from the C:\ drive, then I rebooted it. An error message came up but before I could read it the tower rebooted. Now it only loads half way on the splash screen and f2/f12 don't work. I've tried:

Restarting
Changing the hard drive
Pulling out the CMOS battery
Turing it on without the CMOS battery, hard drive, or disk drive, all at once
Attempted to use a live CD

And in every situation it's the same thing. Black splash screen loaded half way. Any suggestions?
Also, Windows 10 OS.