My 2-month old laptop is already behaving like it's 7 years old

I got my HP Pavilion in October 2015 as a birthday present. It's 1TB HDD, 8GB RAM, Windows 10, AMD A10 processor, 64 bit.


It was working really well for a little while, but a few weeks ago I started noticing problems and now... well, they have gotten much worse.


THE FIRST AND MOST IMPORTANT ISSUE is this: I cannot install new software. I've been told no with everything from Paint.NET to iTunes. I try and install something and it tells me 'Something else is being installed'. Now I usually suspect AVG of that sort of problem. But I tried to update my AVG antivirus and that gave me the same error! It's very annoying as I've just bought a brand new iPhone and I can't get any music or films onto it without iTunes!


The problems have been seen everywhere else too- requests are not being dealt with. If I want to launch an external application from the web (say, downloading content), the application opens but if I'm saving something the wizard won't load.


Another alarming issue is that USBs are now not being recognised. I plugged my old phone in and it kept disappearing; and Windows was unable to read its contents even though I then used my stepdad's PC and it worked fine.


It's slowing down too... vastly. It takes it a long time to think about anything and recently battery life has dropped a small amount.


I have done too whole computer scans now; everything coming up roses and saying there is no problem.


People have sent me ways to deal with some of these issues; but none of them work on Windows 10- everyone I've spoken with so far is still in version 7 or 8 mode.


I'm relatively clued up about maintenance. I CClean, Defrag and use Registry Easy occasionally to sweep up problems but none of this is working. My main concern is no being able to install new software.


It's annoying because my old PC went down a very similar route to its death- but after 5 years. This PC has lasted just 2 months and seems to be on the slippery slope...


I'm quite interested in development- and game design. I have Unity, Visual Studio and all of the Adobe Suite installed. Don't know if that contributes to it or not. Also, I have Steam installed and that's always doing something. Should I remove that??


And that's just it I guess...