My Dell Venue wont "Boot"

I recently went to power on my tablet (it only turns on half the time and when it does) it gives me an all black screen with some words in the corner saying “no bootable devices found" and “run a diagnostic check". I ran the check and nothing was wrong aside from something with the harddrive, yet it still said everything was fine when the test was complete. It was working just fine a few days ago. The only thing I think could be the problem is I've been using an undersized power adapter, since as soon as I got the tablet for Christmas (which was last year, by the way) the charger broke and I had to buy a new one. The only thing I do on that tablet is draw and make art, and occasionally watch videos or listen to music. Can anyone help me? I don't want to pay hundreds of dollars to fix the stupid thing.

Thanks,

Charlie