How to provide password to systems before booting OS completely?

1. Open User Accounts by clicking the Start button , clicking Control Panel, clicking User Accounts, and then clicking User Accounts.
2. Click Manage User Accounts. ...
3. On the Users tab, click the account you want to create a password for, and then click Reset Password.

If you are using Linux red hat you can edit grub.conf file and add a password 

Best option is you can go for BOOT password which can be enabled from BIOS setting.

use BIOS password ... the procedure differ from vendor to vendor 

These passwords are set in your BIOS settings screen. On pre-Windows 8 computers, you’ll need to reboot your computer and press the appropriate key during the boot-up process to bring up the BIOS settings screen. This key varies from computer to computer, but is often F2 or F1. In the BIOS settings screen, locate the password option, configure your password settings however you like, and enter a password.

Configure console or line vty password to prevent anyone from accessing the device