Desktop when connected either by Ethernet or wireless kills entire network?

[Reignman1]

Going on 4 days now and 4 techs including 1 at house and still not fixed by xfinity. No new devices, 1 cell phone, 1 laptop, 2 tablets all connected wirelessly. Desktop was connected via older wireless tenda brand adapter to open network since if I enabled PW it wouldn't connect.

Problem started 4 nights ago when I was using desktop, gf was using laptop and box came on screen and ipconflict and killed network, nothing worked. And ever since has been very intermittent on all devices. Tried new router few days ago and worked for rest of day fine and then in morning all was dead again. Today xfinity tested line first and said it goes from great signal to dead and then back to great so replaced all coaxial cables and reconnected....nothing. He finally said something must be wrong with Ethernet port on desktop because when he disconnects, entire network is fine so left saying needed to buy updated adapter that can connect to AC type router.

Figured why not try removing security key, make it open network and try to connect with existing adapter...which it does but again kills entire network.

So whether I connect desktop via Ethernet or WiFi adapter....kills network.

Tried numerous antivirus and antimalware and although deleted few things nothing has changed, still same issues and have gone through 3 different routers from xfinity

 

[Alabalcho]

Malware on the desktop?
Aggressive torrent client?

 

[jsmithepa]

if 4 techs including a house visit couldn't fix it, I dunno how any1 of us can do anything here. Not even a pico idea.

 

[Reignman1]

if 4 techs including a house visit couldn't fix it, I dunno how any1 of us can do anything here. Not even a pico idea.

Well "techs" over phone from xfinity basically just make sure it isn't on there end to the router. Tech that came out replaced wiring because said was old and then thought figured problem by saying I was getting "feedback" from Ethernet cable or port on desktop because when he disconnected it from router, everything else worked fine again. But after he left I tried connecting via wireless adapter and having same issues...as soon as desktop connects to network via either Ethernet cable or wireless adapter, its killing entire network.


Also so far I've ran rkill first then malwarebytes, combofix, adwcleaner, sophos virus removal to eliminate virus or malware but I do not run a antivirus on this pc usually. Could one have changed a setting that I'm not seeing? I've checked host file, made sure automatic settings were checked under ipv4 and ipv6. When I run Windows diagnostic on pc when connected it either says gateway not responding or something to that effect or says your appear to be connected to the internet but the DNS server is not responding.

 

[Reignman1]

Forgot to include that when I connect to my cell phone through hotspot, it works fine as well. Issue must be within that net work and the desktop...I'm not very network tech savvy so if there's basics I can try, like to check for ipconflicts?

Also noticed there is a new listing when I look for networks called "other network" that was not there before and has full bars. Usually neighbors are 1 maybe 2 at most so must be coming from router?