Gotta check the BIOS first. Your upgrade shop may well have SNAFU'd things when doing the upgrade. Hush my mouth, but maybe even deliberately if they worked out you didn't have a clue.
It's not really frightening. My son's only a couple of years older than you so I know you'll be able to handle it (mind you he started on PCs at age 2, playing Doom2 while sat on my lap).