Exactly what model is your computer? We can help you find a bootable diagnostic which can really help. I don't think this is a RAM problem because that would cause a blue screen of utter death, but the diagnostic would determine that.
I've seen this happen when certain anti-virus software is updated, like Avast for instance. So has anything like that recently changed?
Now did you say you reinstalled Windows? Has that finished? Explain this more thoroughly and describe the screen where it hangs.
If you reinstalled Windows and the problem still happens then it's got to be a hardware issue. When you formatted your disk, did you do the long or quick format? The long way will examine your hard disk entirely for any corruption.
Finally, is there anything plugged into your laptop, anything at all? Mouse, external monitor, etc.? That could be your problem.