If you forgot your computer and you are locked out fo your computer, you can reset the forgotten password with software, or you can try the following ways to bypass the locked computer.
Tips: To reset forgotten password for your computer, see this guide How to use Windows Pasword Geeker.
You can use software to create a new user account which has administrator privilege besides resetting the forgotten password with software. Windows Password Geeker is a password tool which can help you create a user without any old user account and password. You can see the step by step guide in How to Create a New User Offline.
WinPE is a mini Windows system which has the same GUI as Windows, and it can be installed on CD/DVD disc or USB disk, so you just need to boot your computer from CD or USB disk to run a WinPE and get into your computer.
Steps to create a Windows XP PE disk:
1. Download a Windows XP PE image .
2. Burn the Windows XP PE image to CD or USB disk. More information, see How to burn an ISO image to CD or USB disk.
3. Boot your computer from the Winpe boot disk. See How to Set Computer Boot from CD/DVD-ROM via BOOT Menu or BIOS, or How to Set Computer Boot from USB Flash Drive via BOOT Menu or BIOS.
4. When Winpe boot successfully, you can get into your computer.
If your windows is xp, you can try to bypass the current account by login with administrator account. Administrator account is a default account which is created when the windows is installed and has blank password. Boot your computer from safe mode (Press F8 when power on computer), and you will see administrator account shown on logon screen. See How to bypass windows xp password by safe mode.