I just finished upgrading Windows 7 Pro to Windows 8.1 Pro. I thought it was supposed to keep all files and applications, but only a few of the applications were carried over. Seems like I have to re-install most of the programs, especiall games, Office 365, and Microsoft Visual Studio. All the data, such as My Documents and downloads were kept.
Now I'm pissed -- the reason I elected to Upgrade instead of Full Install (e.g. erase hard drive and start from scratch) was so that I wouldn't have to reinstall all the apps, many of which require licence keys.