1. Try scanning for and removing malware. Part of your PC issues sounds like an infection but it could be hardware which you can be sure if you read and do step 2.
Scan with Grif's list at http://www.cnet.com/forums/discussions/how-to-remove-pup-option-603542/#post-f742c795-5881-433b-a29b-6d758efe5cd3
2. After you have made another full backup of what you can't lose, reset the machine to it's factory condition. If it's hardware the problem will remain and it's time to consider if it's worth repairing.
Hello everyone, I have a Dell XPS L702x laptop about 4 years old, never modified any of it's components, never had major problems with it before. Two days ago I cleaned my mouse forgetting to turn the laptop off first, and then noticed a bunch of opened stuff on the screen, didn't pay much attention, just closed them all and also did a restart. When it restarted, it displayed my desktop all right but I got a notice on my antivirus that the "identity component is not active", internet was not working and when pressing ctrl+alt+del instead of showing me the usual options it had blank places to fill in with login information. I shut the computer off, turned it on again the next day and the problem was there again for a few minutes then spontaneously solved itself and I was again logged as the (only) user as usual. But ever since then my 1 key on the keyboard doesn't respond unless I keep it pressed long enough and it starts making a whole row, and ocassionally it also happens with keys 2 and 3 (and right now when writing this post the 1 key suddenly started working normally and the 2 is problematic instead, it just keeps fluctuating randomly). Also, when pressing shift+ the necessary key to type the symbols > : and ? it also pastes whatever text I have copied in addition to the symbol, so I need to delete it afterwards. This is very annoying when typing and also makes gaming impossible, can anyone can help me fix these weird errors?