i have an android htc one sv, it has an internal storage of 4.46gb when i DL an app it says i have insufficient storage, yet when connected to a pc my pc sees 4gb in total with 3gb free, when the phone is powered on it shows 4mb used and 5mb total now i have only my htc phone specs, google51mb, boost zone my default carrier and their services 37mb, earth,  ebay 11mb, facebook 170mb,gmail 10mb, google app 51mb, google play serv 104mb, google play store 26mb, htc back up 5mb, sync mngr 2mb, face book messenger 29mb,offer up 40mb, and talk back 6mb, vdm client and voice mail total 15mb, now since i dont use google earth, i have disabled it, and uninstalled it, total freed up 3.11mb, 

now in total on my phone on internal storage alone not including my sim card which has only pics from my camera on it, the above some equals 557mb where is my other 4.45gb's at?
Maybe this is due excess cache. I guess before an app is installed on to our internal storage, Android caches the data to cache memory. So please try to clear it and try downloading again. 

To clear, just go to Storage Management and click on 'Cache'. It prompts you whether to clear and you need to choose clear. Try and reply if it worked.