Hi, first of all my specs are i7 4771 , 16 GB DDR 3 RAM , Asus GTX 760 , 700 W PSU , 4 TB Internal HDD , 256 GB Samsung 840 Pro SSD , 4 TB WD My Book External , 2x 24" monitors.
Now I am on windows 8.1 and I am forced to install Windows 8.1 but I like Windows 7 more. Thing is whenever I install Windows 7 , my windows gets slow and buggy. For example when I am browsing in Chrome and Firefox, the time I am opening a new tab, it takes like 3-4 seconds to just open the new tab . Tried re-installing dozens of time, still same issue. Also any other application opening gets slow. Video playback gets slow. Whenever I install Windows 7 , I face those problem but I love to use windows 7 .
Now I am on Windows 8.1 , and my uTorrent is bugged as hell. The time when I am adding a new torrent from kickass or any other site , it takes like 5-7 seconds to add that torrent. The busy cursor appears. I am using Kaspersky Antivirus. Is that the reason why I am experiencing slow movements ?
I already checked with SuperAntispyware and everything is clean.
So can anyone tell what is going on ? I am simple confused. I would really like to go back to Windows 7.

Thanks for your time.