Built a new comp in January. Originally I had a DSL internet connection, but I changed back to cable (Cox.net). I have Premiere service with 6Mb download speed and 512 kb up speed.
I recall checking the speeds at dslreports to verify... and found the download to be consistently around 5.5 Mbs.
A few weeks ago I noticed (in an online game) that my speeds seemed a little slower than usual. So I checked them about a week ago. Yes... download speed is now around 2.1 Mb.
Tried several things at home... then had cable company check. Their end is good. I replaced modem to check.... still the same.
OK... shorter story... I hooked in my old computer and it gets the full download speeds via my current modem.
New comp.... I tried via ethernet card, onboard ethernet, and usb.... still slow. Comapred all settings.... seem to be correct. Ran virus and spam checks... all good. Removed whatever programs I thought I had installed after noticing this issue.   Still slow.
Checked port usage via 'Active Ports' and find nothing unusual.
 
So.... thoughts.... reformat? Or can this be an issue with my motherboard?
 
AMD64 3200
MSI Diamond Plus mobo
Dual 6800GS vid cards in SLI
WD hard drives .. SATA and Raid'ed
2 GB Corsair DDR400
 
HELP PLEASE!

Getting a PCI network card would be a quick and easy way of determining if the card on your motherboard is at fault.

Your not running Symantic products (av/fw...) are you?

Right now I'm connected via the USB from modem. When I first noticed this I WAS using the add-on Intel 10/100 nic card that I put in, which will still connect, but at this lower speed.  
Now when I try either of the onboard LAN connectors...well...the nVidia one won't connect at all, and the Marvell Yukon onboard seems to only get Limited (useless) connectivity.
 
Not using anything NORTAON now. I run Kaspersky AV, but have tried the connection with that turned off. I've also tried turning off Windows Defender.
I just reinstalled Anti-Trojan 5.5 and it finds no problems either.
 
Because I'm nothing close to an expert, I also REMOVED my nic card to see if it might be bad and effecting this even when I connect in other ways.... but still got the same results.
 
I'm really stuck on this. What sucks is... I can't talk with MSI unless I have the mobo serial number.... which is on the backside... so I have to tear down the system to get that. So... if I can't find a cure, I guess I have to try reformatting... if that doesn't cure it I'll pull the board and run the old system for a while.
 
More suggestions appreciated...  

Put your nicks back in and un install all of the drivers. Shutdown and remove all of the cards. Boot into your bios and see if you happen to have a builtin firewall. If so you got an option. Disable firewall and use internal nic, disable both, and install you pci card one. Note: realtec seam to be a little slower than 3com chips. I don't like running multiple nicks from different mfg, perferability the same chip so only one drive is needed.
 
If you modem supports a NIC conection use it, you will get better performance from the nic. And don't have to worry about the usb latency.
 
Make sure you have the latest drives and a couple of older version if avaliable. I have seen where older ones were faster in some cases. If you are using your onboard, make sure you have the latest chip set and/or bios for your MB.

To rule out a hardware issue you could boot off of a Linux LiveCD and run a speed test from there.  If you get your full 5.5+ connection speed there you know your hardware is not to blame and a windows reinstall may be in your future.
I usually use Knoppix when it comes to quick tests like this.  I have no idea if it will detect enough hardware in your system to get online though.  I'd put that Intel 10/100 card in, any linux distro could detect that thing.

I just dropped the Intel card back into the old computer... and it runs the full 6Mbs download speed there. So I know that card is good... and using the same drivers for it in both systems.
I disabled the two onboards in the newer computer.... used the Intel card and still get the slower speed.
 
This is just a really odd situation... never heard of this before.
 
Since the onboard Intel in the OLD system went dead, but the add-on card works fine there... I guess I can assume (because I am a layman) that even if both onboards in the new system went bad it wouldn't cause this issue when using the add-on card.... yes?
 
If that's true..... I guess I am really pretty close to a reformat.
 
I'm appreciating you guys helping me with this though. Good to know there are still some people out there that do lend a hand.  
 
Is it possible ......  I run an AMD 3200... lightly OC'd to 2.2... Other than this internet issue, the system runs very stable...and cpu temps are around 37c.  THis should not effect my net speed....??  Nothing else is OC'd.
I can't imagine it having anything to do with power. PS is Antec 550w

Having that 3200 oc'ed to 2.2 "should" not have an effect on this but it couldn't hurt anything to lower it back down and test.  I've seen overclocks do some crazy things.

It almost sounds that you are having a driver conflict. If not with the other nics maybe a video, it's odd but it does happen now and then.

Thats true, it is strange how many things end up being the video card drivers.  I even had a version of the nvidia drivers break roaming profiles at work, lol.

I think I FOUND it!!!!!!!!
 
I have been testing at dslreports during all of this. I used the TweakTester there, which gives some specs and recommendations. After the test, and before it gives results, you have to input some info about your connection/system. It asks for your connection speed given in kbps.... and I think this is where I made a mistake.... I was thinking it wanted my UPLOAD speed, which is 512, and I kept making adjustments based on the report using that speed.
 
Of course, I still don't know what happened to CHANGE my download speed..... but I just used 6000 (my d/l service speed) in the TweakTester and it told me to adjust my RWIN to a MUCH higher number than I had.... it suggested something between 56000 and 150000 so I chose 100000..... inputting this number in DRTCP021 (a connection setting tweak program avail. at dslreports).... and retested my speeds...
 
    First test shows me back around 5.6 MB download...and 520kb upload.
 
Now that I have a clue.... I may tweak this setting a bit and see if I can get the same 5.9-6.2 that my other computer is getting..... and at that point, I'll call Cox and upgrade to the 9MB down/1Mb up service.
 
SomBeeeetch!... JUST in time too! I was planning the reformat for tomorrow....Whew!!
 
Any more suggestions regarding this are still appreciated... as well as the help you guys have already given. Go figure though... it's always the dumbest little thing that'll really mess with ya.
I am still far from expert in this area, but I have learned a little more from this. Kick me anyways!   LOL