If you have forgotten your password on your HP desktop running Windows 7, do not worry! Here's a step-by-step guide on how to reset your password:

1. Restart your HP desktop and press the F8 key repeatedly before the Windows logo appears.
2. Choose 'Safe Mode with Command Prompt' from the options.
3. Once the Command Prompt window opens, type 'net user' and press Enter to see a list of user accounts.
4. To reset your password, type 'net user [your username] [new password]' and press Enter. Replace '[your username]' with your actual username and '[new password]' with your desired new password.
5. Restart your HP desktop normally and log in with your new password.

Remember to keep your new password secure and consider using a password manager to store and manage your passwords securely.