If you just typed "550 ti" (space must be there) you'd see it is supported.
*Driver support goes pretty far back. I updated my dad's HP Laptop which had Vista and it only missed one thing, a Ricoh Media reader. I just went to the official site for the laptop and got the proper driver.
So when you update, make sure to check the DEVICE MANAGER for missing drivers.
Also, we weren't aware that you can only keep your PROGRAMS during the Win8 PRO upgrade if you are running Windows 7. He could only keep his SETTINGS and FILE for Vista, but we opted for "keep nothing" and just copied the files we wanted first. I recommend doing it that way unless you have Windows 7 and need to keep everything.