Hi xianiee,
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I understand you have reformatted the hard drive and did a fresh install of Windows 7, but when you start the notebook, it goes to the repair screen and freezes.
Here is a link to Computer Does not Start (Windows 7, Vista, XP).
Once you are able to boot into Windows, I suggest running The HP Support Assistant to look for any HP updates. I would also run the Windows updater to ensure you have installed all the Windows updates.
Please let me know the outcome.