Should I Reinstall the PC If I Lost Windows 7 Password?

Today one of my friend emailed me that he could not gain access into the laptop which he bought from a stranger.
The Email said as this:
Reinstalling windows 7, no password?

I bought a laptop from somebody, and stupidly, I didn't realize that when they were demonstrating how it functioned that it was logged into Guest. The administrator has a password and I don't know it. I have no password reset disc, or anything like that, and I can't do system recovery, restore, or even use the command prompt because only administrators can do that!
I read that I can reinstall windows 7, but how would I  to bypass Windows 7 password? Please help!

Actually, I have no idea on how to bypass Windows 7 password, and then I searched from google with: how to reset Windows 7 password". To my astonish, there are a lot of answers for Windows 7 password reset.

Answer 1: If you got a windows 7 disk with the computer, all you need to do is put it in the laptop and on start up press F12 or F1, this might depend on the computer, and choose to boot from a CD.
If you dont have a CD labeled Windows 7 or Restore Disk, you will either need to go get this fixed at a computer repair shop or buy another disk from the electronics store.

Answer 2: See if you can run this command in the run. type it in the search bar down at the bottom
"NUSRMGR.CPL"
if it works click on the administrators account and set a new password

Answer 3: It is a good advice to reset the Windows 7 password with a  third party software, like Ophcrack, Windows Password Unlocker or Windows Password Breaker etc. They all can reset the password easily and quickly if you follow the user guide. Take Windows Password Unlocker for example, it allows to do your Windows 7 password reset with a bootable CD/DVD/USB.

Answer 4: If you cannot still log on your computer , you can reinstall your computer. It is the last choice for most PC users as it will overwrite much of the information on your computer. Insert the Windows 7 boot disk into your computer's CD-ROM drive and restart it. Once the computer is running, follow the onscreen instructions to boot from disk and to reinstall Windows 7.

Ok, with these info, I think he can easily reset his lost Windows 7 password at once. If you are still confused with the similar trouble, try with them.

Answer 4: