There isn't an OS on the planet that will ever take up 500GB. In fact my laptop only has a 250GB drive and that not only handles my OS, but also all my program data and program files just fine, and I have 100GB left over.
I recommend just the opposite as this person. Put your OS on the SSD, even if its small, and move everything else to a slower drive.
Totally this. I have two systems, both with 128 GB SSD boot drives. OS, Office, all daily used programs/apps installed, plenty of spare room. All the big stuff, games, downloads, all on a large spinner HDD.