Why doesn't my phone work after deleting files from it?

Episode 1347 (1:35:54)

Laurel from Burbank, CA
HTC One M9

Laurel's HTC phone is full, so she started deleting stuff, and now it won't work. Leo says Laurel probably deleted a critical system file, but she can restore the phone back to the factory settings. That would require wiping the phone completely. Before she does that though, she can connect it to a computer via USB and Windows will read it as a hard drive or a camera. Then she can copy the photos off. She can also install an Android File Transfer program if she has a Mac and do the same thing. Then, she can do a factory recovery. The good news is that after that, she can add an SD card to that mobile phone and start saving the media onto that.

Another option may be getting into safe mode on the phone. HowToGeek.com has an article on how to do that here.