[H] Win 8 upgrade install.

[Winterlight]

Last year I bought one of the 25 dollar Windows 8 Pro upgrade iso 
download deals from MS. I am now ready to install it and have a few questions.
I have all ready installed Win7 on another hard drive with the boot 
drive located on a clean SSD ready for Windows 8 to do the upgrade.
Can I boot off the Win 8 DVD and install that way or do I need to 
start the install from within windows 7?
I guess there is no way I can just install Windows 8.1 direct.. can I?
thanks m