1PC Dropping Internet, but it's not the Network Card?!

[takk]

I have one PC dropping packets, not streaming a crossing around the network, and every long transfer times for files.

What is NOT happening.
Router is working, only 1 PC dropping packets
Replaced NIC, still happening
All other PC keeps connections, while this PC keeps dropping
Changed ethernet cables
Not overheating

What is happening.
Dropping packets during pinging to yahoo.com, almost 50%
no packet lose during pinging localhost // IP address
unable or every choppy streaming of media from this computer
transferring files take forever, 10 minutes turns into 4 hours and counting

What I did.
Replace NIC
Replaced Ethernet
Reformatted a few times, and from WinXP to Win7
Recorded ping test to yahoo & localhost & a PC on the same network for several days

What the issue is.
PC starts up, streaming, transfering, remoting works fine for sometimes several days to only a few hours. Then at some point, I am unable to stream, transfer, or remote control correctly anymore. Restarting right away does not help, only leaving it off for a while seems to be the current work around.

Other then replace the whole PC, what is going on here? I am out of ideas. Thank you for reading this long post.

 

[Shockattackr]

Is this Wired or Wireless Internet, Dropping packets is seldom seen on Wired but can drop on Wireless

Edit

Could Also be your ISP

 

[takk]

Shockattackr, It's wired, I am using Cat6 cabling. It's only one PC dropping packets, and no other computers are dropping packets.

 

[Shockattackr]

Can you give a list of the spec on each PC

 

[takk]

The two PCs in my signature are also on my network, the computer I am having issues is P4 3.4ghz, 1 GIG DDR, some low end graphic pci card? I can get more specs in a little while. All PCs are wired and it shouldn't be the ISP as no other computer is getting dropped.

 

[takk]

Still can't figure out the problem with the computer.