Given that your machine is hardwired, you only need to do this to that machine. Your upstream modem will still have the old DNS server addresses but that won't matter because your Win7 machine won't be making DNS lookup requests there anymore.

In Win7, go Start / Control Panel / Network and Sharing Center. In the upper left corner will be a link to "Change Adapter Settings". Click that and you should see a "Local Area Connection". Right-click and select "Properties".

In the list of items, highlight "Internet Protocol Version 4 (TCP/IPv4)" and then click the Properties button below it. The resulting window contains the IP addressing information for your wired Ethernet connection.

The lower half contains the DNS addresses. It probably is configured to "Obtain DNS server address automatically", but make sure it is now configured to "Use the following DNS server addresses". Then enter the following Google DNS server addresses in the two available spaces:

8.8.8.8
...and:
8.8.4.4

Click the OK button and answer affirmatively to all other open windows so your changes are saved, until all windows are closed.

The change should take effect immediately. Fire up your browser and see if your performance is improved.

Waiting to hear your results!