That sounds a lot to me. My Windows 8 installation takes about 100GB, but that includes a few largish programs like Visual Studio.
Your comment led me to research the size of my OS drive. I found a 122GB file created by IOmeter buried in the "Virtual Store" directory. While IOmeter is not installed on my PC, I had run a benchmark with it last night.
True size of the OS after installation, 30GB. Considerably less than I had thought. Thanks!