Problem Workstation running slowly on Ethernet

I have the following problem.

I have two workstations X and Y. They are identical machnes (Acer Extensa E261) running Windows XP SP2 - both only 2 months old
They have the same software and perform the same function - they run an application that connects to a SQL Server.
We were running a gigabit switch. Workstation X wouldn't work at Gigabit speed - it just said it was connected but there were no comms - confirmed with Wireshark. It worked at 100Mbps full duplex, but it worked slowly
Workstation  Y worked with no issues.

We had some other issues so I changed the switch back to our old switch - a 100/10 Mbps switch.
Workstation Y seemed to work faster.
Workstation X seems to be a little slower.
They both had trial versions of Mcafee on them - which I had just removed and replaced with Norton's 2009. The only difference I can see between them is that there is an extra process on the faster one - mcproxy.exe - which apparently is some sort of proxy for mcafee. Please can someone tell me that this is the problem or where I can look to solve the problem.

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I would check the NIC.  Sounds like it might be faulty.  Try not running it in full duplex to see if it improves.  I have seen where a card that can not run full duplex is actually slower.  I am assuming you did the basic trouble shooting, such as ethernet cable replacement?  Did you check the network connection under Start-->Connect To --> Show all connections and check the properties of the connection to see if you are getting bad packets?  Ultimately I would put in a new NIC, you can get them anywhere now a days, Walmart, Staples, Office Max, or any electronics store, rather cheaply.
set the nics and switch ports properties they are connected to the same forced speed and duplex. I suspect that auto negotiation is your problem
james_kinnearAuthor Commented:
I'm not too sure where to check the for bad packets - I found the properties area but wasn't sure where to check. Is there any diagnosis software for testing NIC's? We are in a remote location and I want to be sure that the NIC is the poblem as the machine is under warranty and can only be serviced by Acer personel and I don't want to call them out and then be charged for it.

I tried changing the duplex setting on the card but got no performance difference.

Thanks for the suggestions - I appreciate it.
If the NICS are not onboard, try swapping them.  Confirm that the other PC now has the slow connection and that the slow PC now has the faster connection....

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james_kinnearAuthor Commented:
I Couldn't remove the NIC as it was onboard but sent it to the Acer reps and it was found that the problem was with the NIC
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