Stumped Losing LAN but not WAN

So I've been stumped by this problem for a few days and before I go and replace the Motherboard (BUILT IN NIC) I was wondering if anyone had ever seen this before.

The PC repeatedly loses its connection to my network
I can't access network drives or ping any local computers

- repairing the connection resolves the issues. but it fails again any time between 15 minutes - 4 hours
- I can still ping the computer & access via VNC using subnet IP
- My VPNs remain intact as does the internet.

Steps I've taken:

- Its not an IP Conflict.
- Deleted DNS & Active directory record & readded
- repatched cable to new wall port
- repatched cable to new port on the switch
- updated GPO & DNS manually
- reset tcp/ip manually
- reset profile

From what I can determine its a DNS issue but im having a hard time determining if its hardware or software related. Its Windows XP SP3. Its the only computer I am having issues with. Any thoughts would be appreciated. Gonna do a reinstall & winsock before admitting hardware defeat.

Does it do it even when you aren't doing anything on the PC? If so I would prolly try winsock and if still no love. Hirens into MiniXP and see if it drops out in there. U have tried OpenDNS? 208.67.222.222 208.67.220.220?

WinSock XP Fix Freeware download and reviews from SnapFiles

Give that a go, bear in mind you may need to reinstall windows if it doesn't work.

yea I did winsock, actually never heard of that software before Dan told me earlier today. but I guess I never used to do much system admin.

Ping return has been solid for an hour. Spose ill leave it till monday & see if connection was lost. most annoying problem to troubleshoot ><

I've seen this sort of problem with phantom network ports, the computer decides to start using a network port that isn't there as a physical connection. Last one I had was traced back to the horrible that is the driver/software with Telstra USB 3g modems. You can sometime see them with a ipconfig /all

winsock XP might cure the symptom but it is always to try and track down the cause.

Yeah go into device manager, click view --> show hidden devices, delete everything under network and then hit refresh to reinstall it all.

The 6to4 adapter in there can often cause this.

Could be a DHCP lease issue?

Ok just to let you know

I left the computer on all weekend and came in on Monday the network was lost again so winsock didn't fix it.
Yesterday I followed Wraths advice & deleted old registry entries which were still there.

Came in today and computer is working still. So I think its resolved.