HELP! Installation Not Taking.

as of right now, i can only run my computer thanks to a back up Ubuntu Mate USB i had lying around.

I was gifted an older computer from a company i used to work for. I had installed ubuntu along side the windows for office and everything was working fine for a while. after a few updates and new installs, i noticed that i messed up along the way and now although i had the option to boot in windows, it no longer was functioning. During my most recent sytem update, i decided to change from ubuntu to ubuntu-mate. Since the windows was no longer working anyway, i chose to erase everything and just install ubuntu mate (instead of installing along side, as i had before)

This is where all my trouble has come from. Something went wrong during that intial install and the computer froze. I figured i could just run the install again and it wouldn't be an issue. The install seemed to work just fine, no error messages. But when i restarted my computer, it told me that there was no OS detected. I ran ubuntu-mate and tried to install it from there, and i did get a error message, something about being unable to write vfat to the device ( i'll gladly upload a picture if i see any activity on this thread).

I ran install a few more times, with a few different ubuntu flavors. Each time it seems to take, and even recognizes that i had tried to install previous versions, but every time i try to boot up my computer, i get the No OS found message.

I'm a total Linux newbie, and i've seen some messages that said to use Gparted to format the drive, but honestly i have no idea what i'm doing and the more i look at gparted, the less it seems i know how to use it. I'm really hoping i didn't just ruin my home system, because running off of an emergency USB is getting really tiring.

i know this is a bad description, and i'd be happy to update with pictures of the errors and all that, but i'll need to see some kind of activity here before i invest the time