Well, i did system optimization with years used tool, Advanced System Care, version 8 by IObit. I did same things i did on other PC running Windows 8.1 (both x86 and x64) without issues. Here are problems it caused: 1. Hard to read window names 2. Unsharp minimize and close buttons 3. Totaly messed text in tabs, navigiation bar and context menus in Chromium (Chrome) browser 4. Font smoothing was also bit messed Here you can see Somebody had similar problem or know how to fix it? BTW: Windows 10 TP, runs fine. Fast. After un-pinning apps from start menu its usable like before, charms and other metro bloat disabled. New icons are bit ugly, maybe if everything will use same scheme it will look better. They should also give option to disable that network connections metro bar and just open network and sharing center. EDIT: I've fixed it. Create new user, log on, with regedit, export keys about desktop, themes, personalization, etc. from HKCU (about 10). Log on to previous account, remove these keys, and merge exported .reg 's. Reboot and it will be fixed. If you just delete these keys and let them recreate, you will have empty start menu / start screen, metro style PC Settings will not work and so on.