Hi not sure if i can help with this one
I am assuming you have tried this...
1st your internal storage .94gb is correct
2nd for your music etc have you downloaded the latest HTC Sync Manager(1.0.39)
for HTC One series & HTC Desire C phones of the HTC web site
The HTC Sync (3.2.20) did not work for me
Start Latest HTC Sync Manager select option sync manager from phone screen when option are available
the next bit took a long time eventually the phone and HTC sync manager are linked together then you can select music photos etc you will have to add music the the sync manager then sync the music to the phone.
If you have a SD card you can select in the settings where to sync phone or sd card this will be under the edit function when you select the phone icon top right
3rd option when using the just the cable Connect HTC Desire C to your computer, and select the Disk drive mode and done.
on the pc your drive will show up as HTC Storage (?
double click the icon then you will get a list of folders select mobile, double clicking to open and you should have two folders gallery and music
open the music folder then drag your music to the empty folder (do same for photos in gallery)
close the folders back to disk icon right click and select eject to remove the folder from your system
allow phone time to find music and load it into the player
Hope this helps