As the title states, I've been having issues with packet loss on my desktop, but not on my laptop.

I'll state right off the bat that I'm not that proficient with computers, outside of pretty basic concepts, so I probably haven't tried every possible solution to fix this. However, I will explain the situation to the best of my capabilities, and what I have done to try to fix it.

After having my desktop packed away for a really long time (couple months), I took it out and set it up again. I remember previously, the desktop had experienced minimal, if any, packet loss before I packed it away. However, when I booted it up again and started running a couple games, I noticed my ping was substantially higher than I anticipated. I did some quick tests and found that I was getting around 5-10% packet loss. I tried resetting the modem and changing the cable, but the problem persisted. To make sure it wasn't just a crappy day, I tested it on another day, and I got the same results more or less. I then tested it on my laptop with a wired connection from the same port and same cable as the desktop, and I had no packet loss and a substantially lower ping. This leads me to believe I have a hardware issue with my desktop. I updated the NIC drivers and tested it again and the problem still persisted. I tampered with some of the NIC settings, namely the Speed & Duplex setting (recommended on a quick google search for a similar problem somebody experienced), and still no changes.

Hardware specs are as such:

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System Information
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Time of this report: 2/6/2013, 19:56:35
       Machine name: 
   Operating System: Windows Vista? Ultimate (6.0, Build 6002) Service Pack 2 (6002.vistasp2_gdr.120824-0336)
           Language: Japanese (Regional Setting: English)
System Manufacturer: System manufacturer
       System Model: System Product Name
               BIOS: BIOS Date: 01/14/09 10:57:16 Ver: 08.00.15
          Processor: Intel(R) Core(TM) i7 CPU         920  @ 2.67GHz (8 CPUs), ~2.7GHz
             Memory: 6134MB RAM
          Page File: 5471MB used, 6986MB available
        Windows Dir: C:\Windows
    DirectX Version: DirectX 11
DX Setup Parameters: Not found
     DxDiag Version: 7.00.6002.18107 32bit Unicode

And the NIC are Marvell Yukon 88E8056 PCI-E Gigabit Ethernet controllers.

I have no idea what could have caused the problem, as the computer literally sat untouched for a couple months before I used it again, so I'm completely stumped as to what the problem could be. Hopefully somebody here is good with networking cause I sure as hell ain't :/

If it's hardware then it's the NIC, so try plugging a network card in - if you want to. You can buy them for a few dollars from local shops, anything will do.

Replacing the NIC fixed the problem. You'd think a several hundred dollar motherboard would have decent NIC installed.

Nope.