How to install GNU/Linux on a Windows PC without the BIOS password?

Follow these steps:

1. Start up Windows just like you normally would, and download the latest (non-test) version of Plop Boot Manager here.
2. Extract the zip and open the folder "Windows" in it. If you have Windows XP, double-click the file InstallToBootMenu.bat. If you have Windows Vista, Windows 7 or Windows 8, right-click the file InstallToBootMenu.bat, click Run as administrator, and then click Yes when prompted. You should now see this: Press y, then press Enter. Wait until installation is finished and press Enter to close the window.
3. Restart your computer. You should now see something like this (if not, restart your computer again while hammering on the F8 key, and when a menu appears, select "Back to list of operating systems" using the arrow keys and press Enter):
4. Press ↓ to select Plop Boot Manager and press Enter. You should now see (something like) this:
5. If you are trying to install using a CD or DVD, select CDROM using the arrow keys and press Enter. If you are trying to install using an USB-stick, select USB using the arrow keys and press Enter (If your computer freezes after choosing USB, restart your computer, select USB using the arrow keys again, and this time hold shift while pressing Enter. If it still doesn't work, try a different USB port and try again.).

Your computer should now boot from your installation CD/DVD/USB-stick. Good luck and enjoy your new operating system!

If something doesn't work or you need clarification, feel free to comment.