I had AT&T 3MB dsl for a very long time and it worked really well transfer rates at 250KBPS very good for where I live. They forced migration to their U-verse 3MB platform in November and the service kept taking out my moden so almost everyday we had to reboot the modem and just on my computer my data transfer rates dropped down to almost nothing 10KBPS approx, once in a while I would get 350KBPS and other times 5KBPS my computer was hard wired with this service, in December I changed out my HD to a Samsung SSD just a FYI, all my other devices have great transfer rates and are wireless. I now have cable internet 15MB service and all my other devices work great my Iphone uploads at 3MBPS and downloads at 13.5MBPS as per speedtest.net I put the wireless card from one of my other computers in my main computer and the transfer rates are still poor, so I know the problem is in my main computer. I have taken my computer apart cleaned and put everything back together I have tried many different software programs that say they can fix issues to no avail.
I built my computer for gaming about 7 years ago, I still have one I built from 15 years ago and it is still working great and speedtest 10down and 2up. WII streams video from Netflix no problem X-Box too same with phones and laptops.
My main computer has a MSI MS-7125 V.1 motherboard, CPU AMD Opteron dual core 2.61, MSI 6600gt video card, 2GB ram and a Samsung 250GB SSD HD, Raidmax modular power supply 630watts running Windows XP pro.
Any ideas on what to try next; except for downloading from the internet my computer runs very fast I don't game anymore but need to upload and download photos and large files?
More info: I use my Iphone side by side connected with the same wifi system in my house and my ping will be about 16, my download will be about 14.5MBPS and my upload will be 3MBPS and on my computer ping 159, download 1MBPS, upload about 1.5MBPS. My 15yr old computer using same internet and same wireless card ping 40, down 7MBPS, up 2MBPS. All tests run within seconds of each other. I have run Ccleaner, full deep scan with Trend Micro, defrag and error checking.
Start with the simple stuff. Try bottling on a disk like hirem boot cd and use there mini xp boot to see if the error still there. If it not. I would scan for virus and malware. If there are none try using ms config and use the start up tab and turn every thing off there. It could be a issue with a program or you have more then one firewall or anti virus program running.
Since you have 2 computers you can try a old program called IPERF. It is a very simple line mode program that run in memory only. This mean it pretty much just test the network and the drivers in the OS. This will eliminate large parts of the OS related to the disk subsystem. It also is much easier to get consistent test results as you make changes than testing to a internet based server.