How to enter you computer if forgot password

First way

1. Reboot your machine.
2. Press F8 before the Windows boot screen appears.
   • Do not press F5 as used on the NT/9x series of Windows.
3. You will be be prompted with a boot options menu.
4. Select the Start Windows in Safe Mode option.
5. Click through several self-explanatory screens until your reach the familiar 'Welcome' screen.
6. Note that this welcome screen is limited to 256 colors and 640x480 resolution because the primary graphics will have been set to the Windows Safe Mode software VGA adapter. You will not be able to change this mode even in Display options, while Windows is running in Safe Mode.
7. Find the icon for the Administrator user. If the default settings of your system haven't been changed, there should be no password for this account.
   • The Safe Mode Welcome screen might display some of the other users on your system.
8. Login as the admin.
9. Press Yes at the prompt asking if you would like to continue using Safe Mode.
10. Continue on to the User Settings control panel. Here you can change any of the other passwords for user on the machine. Make any changes you want.
11. Reboot your computer. As long as you don't press any keys (i.e. F8) during the boot-up the computer will startup normally.
12. Login as the user for which you set the password.

  If it doesn't work above , you can try to use windows password reset 6.0 or OPHCrack (for free)
to crack your windows password  without erasing anything.

Second way

1. Login to a computer that can connect to the Internet. Download Windows Password Reset Tool and decompress it on that PC. Note that there is an .ISO file. Burn the .ISO file to a CD.
2. Get out the newly created CD and insert it into the locked computer.
3. Reboot the locked computer and then follow the process of instructions. Just a few steps, the old password was removed.
4. Setting new password:

Step one: Open the "Control Panel"

Step two: Click the "User Account "

Step three: Select the account you wanna to set a new password.

Step four: Click "changing Account " and "set up password", then fill out the form as listed. Click "Create Password".

Thus, you have a personal login ID and Password, anyone has no right to login to your computer without this info.

Third way

1. Open Command Prompt. If you don't know how, open the Start menu, go to Programs (or on Windows 2000 and up, all programs), go to Accessories, then you'll see Command Prompt, click it.
2. You'll see a black screen pop up.
3. Type in: "Net User"
4. It will then show you a detailed little chart of all the User Accounts on the computer.
5. Choose which account you want to hack.
6. Say it says the user accounts are: Owner, Administrator, John, Alice, Christopher, and Guest.
7. You choose Alice (Say you wanted to annoy your wife or girlfriend, I told you this would be a useful guide ;) ).
8. Now type: "Net User Alice", it'll give you A LOT of information about the account. This step isn't necessary, but it gives you information on other things you can do to the account, such as set it as innactive and delete it.
9. Type in: "Net User Alice *" It'll tell you to enter a password, then again to confirm it. This will both change the password or make a new one.
10. Good Job! You've actually hacked an account! Now if Alice says anything, good luck with that, that's in the article "How to Ignore an Annoying Wife or Girlfriend"... if it exists.