Phone wont turn on or charge, but makes a chime when connected to my PC topic

Hey so two days ago my S3 crashed and wouldn't turn on again. I've tried the home button + vol up/down +pwr and nothing. I've tried putting i another battery, still nothing. When I connect it to my computer it makes a chime so its recognizing it.

I bought the phone from a friend like a year ago it was rooted and was running task650s rom. It hasn't been updated for like 6 months though. How can I hook it up to my computer and flash the stock rom if I cant get it into download mode?