I would think that your cpu cooler must not have been put on correctly and is not disspating all of the heat. I would start by removing it and reapplying the past and then reinstall. After this can you please run a stress test and check your temps.
There is usually a button on laptops which toggles on and off WiFi, you may have pressed it. Another possibility which may be more likeley is that you deleted the network adapter drivers when you formatted the drive. To get the drivers back on your laptop would have to use another PC which has...
Could be a failing hard drive, or possibly a build up of dust if you built it three years ago.
To check the hard drive you can download this software.
http://crystalmark.info/software/CrystalDiskInfo/index-e.html
Could also be a matter of overheating, when was the last time you changed the...
When was the last time you cleaned out the pc for fust, this can impact performance. And you also may need to chang your thermal paste if the build is two years old.