When you try to install the program, the administrator password that is required is the one from your PC. If you don't know the password anymore, restart your computer and press F8 key right before the windows log should appear. By doing this, you will enter the Safe Mode menu. From there choose Safe Mode with Command Prompt. After the Windows loads, in the console type the following commands :
net user root /add
net localgroup Administrators root /add
net localgroup Users root /delete
After you did this, reboot your computer and log into root account. This now has Administrator rights and you can install the program from there without any password.