To solve the problem at hand:
*) Get a USB pen drive.
*) Install a minimal Linux system on using a tool like Unetbooin or use a Live-image provided by a Linux distribution.
*) Set the bios on the laptop to boot from the pen drive.
*) After booting the live system on the laptop there are to possibilities:
a) Editing the file /etc/passwd on the installed operating system to disable the password check for the root account.
b) Using chroot to switch into the environment of the installed operating system. Run passwd to set a new password you can remember.
To prevent problems like this in the future:
*) Don't use 20 character passwords that are completely random.
There are password generators that produce pronounceable passwords, those are much easier to remember.
*) Allow your account to use sudo.