Resetting BIOS defaults will not fix most computer problems. It's possible that your CMOS battery was going bad. If you run into the same error again, open the computer case, use a grounding wrist strap, remove the button cell battery, and replace it.

You might try actually learning what the different screens are called rather than calling it a "screen like this".

There are very few computer problems that can be fixed by deleting anything... so your title doesn't really say a lot. The only computer problems that I can think of off the top of my head that can be fixed by deleting something would be malicious files. (AKA viruses)

If you are really interested in computers, try reading some more instructables about fixing them, and possibly take some classes before you try to write about something you don't understand. My Dad has been known to say: "It is better to be thought a fool, then to open your mouth and remove all doubt.".

(Understand that I am not calling you a fool, but there are a lot of people on this site that know a whole lot more about computers than even I do, and I used to do data recovery for the US government. Things that you say by accident can seem pretty foolish to some people.)

Good luck in your journey into the computer repair world... it's one you will never forget. :)

I don't think all PC boot problems stem from whacked-out BIOS settings.

Press F5 instead of F10. Fixes the problems more simply than fiddling with BIOS setup.