One PC won't play w/ router, others fine, HALP!

[pirahna1]

This is a really strange problem, I'll start from the begging.

I own a Linksys wired router. I have used it many times in the past. In my previous home I used it with Comcast Cable net and my PS2 and a few PCs. Then we moved and I used it with Verizon DSL and the same PCs along with VoIP. Both of these instances I've never had to enter the router settings menu, it's always 'just worked' no questions asked. Now we've moved the third time and the problems start. However the problem is not with my router...

My mother-in-law's PC is the culprit. She had Verizon DSL before we moved in. She had the modem directly connected to her PC, everything worked honky-dory. Once we moved in and installed my router her PC stopped connecting to the internet at all. My 2 PCs and my PS2 worked flawlessly, but her PC just would NOT want to work with my router. I spend about 6 hours on the phone with the techs at Verizon and Linksys, and finally got a resolution. I believe we set the router to PPoE (for DSL) and hard-coded the DNS into her PC. The tech told me that since our IP was dynamic, I would have to re-code her DNS entries every once in a while, which we never had to do for some reason or the other.

However, we just switched over to Comcast cable. Once again, her PC will not connect to the internet, while all my devices work fine. However, her PC WILL find files on my 2 PCs and we can swap files back and forth, and my router is finding her PC, so they seem to be interacting. I removed the PPoE from my router and DNS entries from her PC. I called Comcast, they could do nothing to help (we tried re-coding the DNS, IP, etc etc, nothing worked). I called Linksys and they gave me some bullshit that I had to pay them 30$ to even talk to me because my router was out of warranty (even though it was out of warranty last time I called and they helped me, well, at least they talked to me lol).

I tried to run my router software on her PC, however it says that it cannot find the router and to check the cables, blah blah, everything is fine. I triple checked it all. It just seems like her PC won't play nice with my router even though she can share files. Could she be missing some sort of file on her PC? This is what the first tech at Verizon hinted at, and which is why we had to hard-code her DNS. Please note, the Comcast tech had me hard-code the DNS to no avail.

Her PC was bought by her sister, who reinstalled windows so many times I'm surprised the PC hasn't imploded. This is what leads me to believe there might be a file missing. Should I even try to call M$ or will they give me a BS answer? I can't call Dell, because we are not the original owners and they won't troubleshoot with us (I think this is retarded).

I hope my post was clear enough. This problem is very annoying and just overly complex. Why would it work with PPoE/ DSL but not cable internet? Are there any other options/suggestions/do-it-again-the-right-way-this-time I can try? Is the problem so simple that both the Comcast tech and I passed by it? I'm generally a nerd when it comes to PCs, but not so much (read: granny-like) at networking. Any help would be amazing and I thank you in advance. If you need me to clear any of this jumble up, I'll do my best to re-explain what you need me to.

Once again thanks and many an internet to whoever can help!
tldr; I know, but it's really that crazy

[Killgannon]

I work at an AT&T DSL Call Center so here i go

Firewalls? is she running one? antivirus could cause this too, if this just recently happened like "omfg tonight" and she's running mcaffee they did release an update that broke peoples stuff... im serious... but apparently they fixed it now...

the next thing is goto Start > Control Panel > Network Connections > right click the Local Area Connection > Properties > select Internet Protocol TCP/IP > Properties > Make sure she's not using a static IP Address (though if you're sharing files this shouldnt be a problem)

go Start > Run > cmd > in the black dos box do ping yahoo.com > if you didnt lose any packets then she has internet connectivity but somethings blocking her browsing

next thing reboot, as its coming up hit the F8 key (thats the one on the top of the keyboard not f & 8) and it should bring you to a boot menu, one of those selections should be Safe Mode with Networking, select that, let it boot up, once it comes up (yea itll look crappy sorry =/) try to browse if you can browse here, but not in normal mode there's a PC issue, if you still cant browse here there's probably still a PC issue and a reinstall (fresh ie fdisk the hard drive...) will probably fix it

(if verizon and comcast didnt do this they make me sad :()

another thing you can try is doing an ipconfig on your pc thats working, and then on her pc and compare default gateways... but even here its still at the fact that you can share files, so she's still getting a correct ip from the router and the gateway should be the same... (because file sharing goes through that router too... and if she can share and stuff locally she's fine with the actual local network, out to the router at least, and your connection is fine since yuou can surf else where and be happy)

your biggest things are:
Firewall
On her pc specifically, maybe she accidently blocked something or something safe mode will stop these from running

Some kind of Virus
Again on her pc, safe mode will tell you this most likely

like i said before, if you can run fine in safe mode on her pc she's got an issue and your best bet is to fdisk and reinstall unless you absolutely want to go through the horrendous troubleshooting of finding what process is blocking her internet

The tech told me that since our IP was dynamic, I would have to re-code her DNS entries every once in a while, which we never had to do for some reason or the other.

is bs btw... dns servers should rarely if EVER change.