Internet connection drops frequently

[Mudar]

A week ago.

[Lord_Nikon]

How did you go about doing the format?
Which programs did you install after the format?
Are you using a Microsoft account? (Using an email address to login to your computer)

[Mudar]

Boot CD, format C.

Programs: office, chrome, skype and that's it. I don't use a lot of programms, as my primary activity is internet browsing.

No I don't have any account.

[Lord_Nikon]

Hmm, very peculiar, the symptoms would indicate malware however after a format it's nigh impossible for malware to survive, something on the computer appears to be changing the dns settings periodically, could try setting it manually, instructions below

http://www.geeksquad.co.uk/articles/how-to-change-your-dns-windows-10

Use these servers
8.8.8.8
8.8.4.4

[Mudar]

I've done exactly as the instructions said, still happens (in normal mode).  

[Lord_Nikon]

Ok, need to disable all non Microsoft services, hold the windows key on the keyboard and press the letter R, should get a Run box, type in "msconfig" and click ok, go to the services tab, tick the box at the bottom to hide all MS services, click disable all, click ok and restart

[Mudar]

I can add something might be helpful, that this happened exactly after my friend plugged his flash memory in my computer, I suspected that his flash had viruses, and I focused on anti-virus removal tools and programms to remove it such as (kaspersky, malware bytes, avira, avast) non of them could detect any virus or harmful malware, finally I formatted it 2 times. Can't understan why it works when I connect it to my mobile data.

[Lord_Nikon]

That is the curious part, in theory if it works on one network then it should work on all unless the network settings prevent it, there is definitely a problem on this computer however. The flash drive could be the source but any virus/malware wouldn't survive a format unless it was brought back again through cloud services such as chromes syncing service or ms account

[Mudar]

OK, I disabled all non MS programs and restarted it. I'll keep you informed about the results. Thanks for your time.

P.S: Could malware be brought back again to another drive if I format only C? If so,  why they can't be detected?

[Lord_Nikon · Accepted solution]

It's possible, if the malware origin file is on a different drive or partition then when the file is accessed the malware can reassert itself on the OS, unfortunately detecting malware is not 100% effective, that's why it's generally recommended to use multiple malware programs, I generally recommend malwarebytes first as that is one of the best, after that I also use spybot search and destroy