Keyboard problem (+ the usual audio one)

Hello there
I've got a couple of problems, and one of them is really weird and i was looking for some help to get past it.

The first problem is one that a lot of people denounced here: the audio not working sometimes. In order to fix it, all I have to do is to hard reboot my pc, and it works again. The sad thing is that I started having this problem right after a technical intervention on my pc. Before this, my old mother board had a serious issue with the GPU, so they changed it and gave me this one. It was a" refurbished" mother board, so i'm assuming that whoever repaired it didn't do his job properly, and so, thanks to him, i inherited the problem. I called Dell support again for that, and they brought yet another refurbished mother board that didn't work at all (DOA, the computer wouldn't even turn on with it), so they reinstalled the audio problem mobo, and one of my RAM modules even got burned in the process (replaced it already, thankfully). thing is, now i'm quite scared of the dell support service (but you know, i live in italy, and nothing works here), and i'd like to avoid it as much as possible. I'd rather have to reboot my pc now and then, rather than allow dell techs to further destroy my system.

The second problem is on the keyboard, and showed up very recently.
Sometimes, a row of keys on my numpad, the 4, 5 and 6 buttons, stops working properly and only work with if I press them very hard. This problem goes and comes, right now these keys are working properly, while just a minute ago i had problems with them. I don't know what's going on, and I hoped that perhaps some of you had this problem and somehow managed to solve it. I'll supply you with as much information as I can.
- My numlock is on
- "Mouse keys" are disabled
- This problem showed up after dell asked me to try solving the audio problem by formatting the system, reinstalling the OS, and reupdating all drivers (it didn't work obviously, as I had already tried it before the intervention where my RAM module got burned). So, I've updated my BIOS from A11 to A12, and updated all the "chipset" related drivers. I remember having a problems with one of them (got an error message telling me that a process coulnd't be started), but everything seemed to work fine anyways.
Do you guys have any idea about what it could be, and if it's solvable without asking Dell to send people to destroy my laptop?

Thanks in advance!

 

If an external keyboard works fine all the time, you need a keyboard replacement. I would suggest replacing the motherboard again to fix the audio issue. I apologize about the inconveniences that you have had so far.

 

yeah, will try that as soon as i get my hands on an external keyboard.
I'll also try to somehow clean it, could dust be what's causing the problem?
I'm asking because I have an handheld consolle (nintendo 3ds) that had a button that shown exactly the same problem, and i managed to fix it completely with a bit of deoxidizer for electronic curcuits. Is it wise to try to do the same on the keyboard?

 

so, can anyone give me an idea or something?