Various problems with Windows 8.1

Hey guys, thanks in advance for listening to my problems.

I used to have a non-legit version of Windows 7. I was pissed of by a lot of things, and decided that it was time for me to buy Windows 8.1. I liked Windows 7, its just that I wanted a legit version and the one I bought gave me the cheapest price, while still being able to upgrade to Windows 10 later.

So, I bought an online version of Windows 8.1, and did a complete fresh install. My entire HDD was wiped. There was no turning back since the version I bought did not allow downgrading back to Windows 7 (Later, as you will find, to my regret).

I installed a few things. This is my current list of programs I installed (Including games):
Starcraft 2
The Witcher 2
Planetside 2
Assassins Creed
uTorrent
PowerISO
Teamspeak
Steam
Google Chrome
Geforce Experience
Spybot
Avast Free
Malwarebytes
VLC
Open Office
Java

As you can see, nothing really harmful. Yes some of the Antivirus may slow down your PC, but not as extremely as the problems that I will explain soon.

First everything went well, played games, everything went fine for about 4 days. That's when it started. These are the problems that I currently have (about a week after installation):

1. Firstly, the task bar + Metro UI is broken. The Taskbar does not respond when I click on it. If I press the Windows-key on my keyboard, it will sort of 'reload and work for a click or two, then freeze again. When I press the Windows-key again, it launches the Metro. This also works for a second or two, then freezes as well. I can move my mouse, but nothing responds anymore. When I click the Windows-key again, I return to my desktop, to return to doing whatever I was doing.

2. Some files are not working. For example, I bought Beyond Good and Evil (A hidden gem in gaming btw, easily in my top 10 games of all time. Critically Acclaimed, but was commercially unsuccessful, find it here).
The file is a installer, a .exe file. When I click it twice (or right click + open, or right click + run as administrator) nothing happens. My mouse turns from a 'pointer' into one of those loading pointers, like found here. This stays for a while, then it acts as if nothing ever happened. When I press the Windows-key, to refresh my task bar (since it is frozen again) it reloads, but there is no new window open, no installer. This isn't just for any file. I also downloaded drivers for my mouse, tried to open them, same result. (These were also .exe.). However, not all are broken. Steam opens, and the opening file for Steam is also .exe but works fine.

3. Some things simply do not work. For example, when I open PC Settings on the Metro (A second before it freezes, as mentioned before) it opens up PC Settings, a bit like this. It stays on that screen, and nothing loads. By pressing the Windows-key I am able to get out, but it will not start the PC Settings.

4. Thats basically it. There are some other small things that may or may not be part of this. PC is a bit slow, and the Task Bar often overlays games or other things. (It did not do that before the problems started).

Additional Information:
- It probably has nothing to do with bad hardware. On Windows 7 my PC was doing fine. My stats are: i5-4690k, GTX 750ti on top of a MSI pc mate z97.
- Ctrl+alt+delete still works, and so does Task Manager. I could not spot any applications/programs on Task Manager that should not be running.

Thanks for reading my post. Any thoughts or questions, feel free to post them. If you have a possible solution, please, oh for gods sake, please help me!