Htc One S data:
Other names :Z520e
GSM frequencies :850 900 1800 1900
Standard UMTS :850 900 2100
Type :Touch
Dimensions (W x H x D) :130,90 x 65,00 x 7,80 mm
Weight :119,50 g
Main display :Color / AMOLED
16M colors
540 x 960 px (4.30")
Standard battery :Li-Ion 1650 mAh
Internal memory :16 GB
RAM memory :1 GB
Operating system :Android 4.0 Ice Cream Sandwich
Processor :Qualcomm MSM8260A
Processor clock :1,50 GHz
How to hard reset:
Warning! All data will be lost!
1.Power off your phone
2.Press together volume down + power button until the buttons from the bottom of the screen will not flash
3.Release your fingers from the buttons and then press again volume down + power button until recovery menu appears on the screen
4.Select with volume button "factory reset" and then press power button
5.Wait until the phone restarts
Here is video how to do: