The Hard Reset
A hard reset is like reformatting your computer. It will wipe everything—your files, personal data, preferences and homescreens, and all your applications on your phone. Of course this may not be too much of a problem if you have most of your important stuff on a SanDisk card—it won’t erase that. Rather, this is like getting a new phone again. You have to go through the same setup, inputting your Google account name, setting up your homescreens, downloading the applications you want to use, and inputting the personal data you want saved.
Thankfully Sprint has made it easy to do on their version of the HTC Hero. Here’s how to hard reset your Sprint HTC Hero:
1) Select Menu > System > Security.
2) Scroll down to the bottom.
3) There you’ll see “Factory Reset." Select this and a button will come up to reset the phone.
4) If you really need to do it, select it. It will then reset the phone and you will proceed from there as if you just got the phone.
There's how to reset your Sprint HTC Hero. Hope this helps!