Folder on start up?

10.4, 10.5 or 10.6 put your install DVD into the optical drive (CD/DVD drive) and reboot. Be sure to either use the disc that came with your Mac, or, if you installed a later Mac OS X version from disc, use the newer disc. As soon as you hear the boot chime, hold down the "c" key on your keyboard (or the Option Key until the Install Disk shows up) until the apple shows up. That will force your MacBook to boot from the install DVD in the optical drive.

When it does start up, you'll see a panel asking you to choose your language. Choose your language and press the Return key on your keyboard once. It will then present you with an Installation window. Completely ignore this window and click on Utilities in the top menu and scroll down to Reset Password. After resetting the password use Startup Disk from the same menu to choose your hard drive for startup and restart.

With 10.4, 10.5 or 10.6 if you don’t have an install disk check this article. http://www.macyourself.com/2009/08/03/how-to-reset-your-mac-os-x-password-withou t-an-installer-disc/

If you're running 10.7 Lion check this article
http://osxdaily.com/2011/08/24/reset-mac-os-x-10-7-lion-password/

With 10.8 or 10.9 restart holding the Command and R keys, then from the drop down
of actions, choose Terminal. When Terminal opens type:

resetpassword

and press enter.

You will get a reset password window from which you can select the user you want to reset, the admin account in your case. Type a new password twice, do not do anything with the hint box. Click Save, then confirm you want to do this reset. Then click apply to the user's home directory, and click the apple in the left corner, and choose Restart.