Changed BIOS settings to legacy boot, turned off secure boot, now my computer won't start up at all

So, my computer had a complete meltdown yesterday. First, it had to "prepare" Windows every time I logged in and wiped all my settings. Then, I booted it into safe mode in an attempt to fix this issue, but couldn't log in because the computer previously belonged to my uncle who gifted it to me, but he doesn't remember the admin password, so I thought I'd change it through an Ubuntu bootable drive. I opened the BIOS settings, turned off secure boot and turned on legacy and exit, but now the computer won't boot at all. Doesn't even give me the Dell logo. Just emptiness for about a minute or two and then it shuts itself off. I don't know the exact make and model of this computer. All I know is that it's in the Dell XPS line. Help?