Basically I bought myself a Dell computer last week, but it has been a very painful experience so far. I am on the verge of bringing it back to the store. I am no computer wizard, but I know a little bit, I have been installing and executing the basic repairs (both hard and soft) for pc's for several years. But now I have ran into a brick wall.
To start off with, the computer I bought is Insprion 3558, it runs Nvidia GeForce 920m, i5-5200u (broadwell) processor, and currently has 4GB of ram attached to it. It came with a OEM os - ubuntu 14.07 (if i remember correctly). When I started the pc for the first time, it seemed a bit sluggish, but last time I had used Ubuntu was about 7 years ago, thus sluggishness didn't strike me as a red flag at that moment.
I had a Windows 7 serial key, so I installed the W7 on it. At first, it was all right, I installed all the drivers that needed to be installed, i got them from here (https://devid.drp.su). Some of the drivers I managed to snatch from the Dell webpage, but not all of them worked (also the automatic updater didn't work as smoothly as it was supposed to).
However, the pc was still super sluggish. The webpages took a moment to load and scrolling them was quite disturbing. After digging around the internet, I found out that there is such a function as speed step enabled by the OEM. After I disabled it, the things went well for a while. Until I noticed that even when the pc is idle (no internet browser, av-software, etc) the task manager shows that cpu is 25% used (This is absolutely not normal). Couple of months I helped my friend to install a similar computer and it is using about 5% with normal internet browsing. When I start Firefox, my cpu usage skyrockets up to 80-90%. This is just absurd.
It could be that I have done something wrong throughout the os installation (or driver). But maybe you have some remedies at hand, what else is there for me to try out. The pc is unusable, if I want to pop presentations, excel files and other cool stuff, it simply wont be able to handle it.
Lastly (i have never done this) but is there a chance for me to return pc to its factory settings (with the os, partition sizes etc.). The store asks me to bring it in a mint state with the original OS in case of return. <- this really bothers me, because I am about to go for a longer vacation, and I won't be able to return this machine afterwards. Therefore, i have to act relatively fast.
I will appreciate any ideas/thoughts/insights!
Edit: I tried turning the speedstep function off and on and now nothing really changes in the load that my cpu has. It is always at around 25%.
P.S. I apologize for my English
Have you tried updating the BIOS and the chipset firmware for your system. Also you can also try a clean boot, that would be disabling all the third party services and startup applications including the antivirus if any. An alternative would be booting the computer to safe mode. If you have any uninstalled drivers showing in the device manager, please share the hardware IDs of the same so that we can help you with the necessary drivers.