There may be many reasons why system freezes. Has your daughter installed/updated anything before problem starts? If so, then you should try to uninstall/reinstall this and check if it helps.
This can be also hardware problem. Check memory with memtest86+
. Check also temperatures using HWMonitor
. Finally check your hard drive, to do this run Command Prompt with Administrator Privileges (Start > All Programs > Accesories, right click on Command Prompt and then select “Run as Administrator”) and there type
chkdsk /f c:
It might display a prompt asking if you want to check the disk the next time you restart your computer. You should agree and restart your computer.
You may also check disk S.M.A.R.T. status with Crystal Disk Info
. Open this program, then click Edit > Copy and paste this here. Somebody will check if everything is ok.