What Grey Alien said: The limiting factor is your ADSL speed by far.
since your ADSL speed is most likely less than 10Mbit anyway, you wouldn't see a difference in your internet browsing speeds if you had ancient 10MBit NIC's in your PC's let alone 100/1000Mbit. (Unlike what the pimply salesguy at your local bestbuy told you, undoubtedlt. Likewise, using a Pemtium chip does not make the internet faster, unlike what Intel's old commercials claimed.)
Anyway, the '1000mb' connection is really 10/100/1000. It will try to connect at 1000mbit, then fall back to 100mbit if your router won't support it, and 10mbit if 100mbit won't work either.
Network connection speeds are rated in megabit/second. Realistic throughput speed's are about 1/10th of that in megabytes. (you lose some due to sart & stop bits, and general packet overhead)
Anyway, Since your good PC still shows a 100Mbit connection, you're not using the 1Gbit speed anyway -- both are running at 100Mbit. Most likely your ADSL router is not gigabit compatible (few are), or your using sub-standard wiring (gigabit ethernet is much picker than the slower standards were) But most importantly, This 100Mbit only applies to the connection speed between your PC's and the router itself -- the router uplink speed is entirely seperate.
Your internet browsing speeds will be limited by your ADSL speed itself, not the local LAN speed. Unless your internet link is faster than 10Mbit (very unlikely, unless your in SouthEast Asia), the only time your individual PC NIC speeds come into play is when you are transferring files directly from one PC to the other over the local network. In your case, that would go at speeds up to 100Mbit (which is a max speed of about 10megabytes/second, keeping packet overhead in mind). Everything that comes in from or out to the internet is limited to your ADSL connection speed, which varies greatly to where you live. for the majority of people, the ADSL connection speed will be somewhere in between 384kbps (0.34 Mbit) to 3Mbit. In some of the big cities they may go as high as 7mbit.
As you can see, not even
close to the 100Mbit that your PC's talk to your router at.
You say that one PC feels slower than the other when it comes to internet communications -- have you tried running a speed test?
For example, go to:
http://www.speakeasy.net/speedtest/ and see what kind of atransfer speeds you get. If they are close to the same, then you know that the connection speed itself is fine.
If one gets a significantly slower speed, you may want to look into that PC a bit closer -- it's possible that you have a bad cable going to it (=packetloss, which causes delays while your PC waits for the information to be re-transmitted). It's also possible that you have different software settings:
- You may have set up one of the PC's to route its traffic through a proxy server. This can either speed up or slow down your transfer speeds, depending on the speed & location of the proxy server.
- You may have some spyware or a virus that is intercepting & parsing all your internet traffic which can slow things down
- You may have a bad DNS server set up on one of the computers, which can lead to delays while it times out and falls over to the secondary server each time you try to access another site or server. This can lead to a ~2 second delay when going anywhere new, which is an annoyling slow response time. Once you hit the server, transfer speeds would still be the same in that situation though.
- You may have some crappy plugins like new.net which hijack your real DNS with their own craptacular versions, so they can sell people 'alternative' domain names. Spyware, with a negative impact on your browsing performance
- Your slow PC may be low on resources, and even though the network card can provide the data fast enough, your PC may have a hard time keeping up with it. What's your typical CPU and memory utilization?
- Are the PC's themselves in the same ballpark, power-wise? Browsing on a 486 will always feel slower than on a bazillion gigahertz system, simply because it takes the webbrowser a lot more time to fluff the received data around and draw all the images, etc. for you. Your applications will have a slower response time in general on a slow computer.
- Does it make a difference if only one computer is turned on at a time, vs. both? If so, then it's possible that one of the computers has something going on in the background that generates a lot of additional network traffic, such as a fileshare program that everyone and their grandma is downloading info from your PC with.
Hope the above clarified some things...