This stuff is a lot more lax than it used to be, no?
I've installed Win7 fine from MSDN media with a branded OEM key
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Maybe a different solution would be to use Toshiba's own tools to do a complete reinstall of Windows 8 on the current hard drive, then uninstall any of the crap you don't want, mount your new SSD externally if possible then use an imaging program to create an image of the current hard drive.
Bit of a hassle I know.
EDIT: Ignore