Hi,
1. What made you to change the MAC address?
2. What exactly happens while you try to connect to internet?
3. Do you receive any error code or error message? If yes, what is the complete error message?
4. Have you checked the issue in internet explorer as well?
Please follow the methods provided below and update us with the results.
Method 1: Run the network troubleshooter and check.
http://windows.microsoft.com/en-US/windows7/Using-the-Network-troubleshooter-in-Windows-7
Method 2:
Please try following the steps provided in the article and check.
Wired and wireless network connection problems in Windows
For more information, refer to the articles and check.
10 tips to help improve your wireless network
http://www.microsoft.com/athome/setup/wirelesstips.aspx#fbid=hq7zl63PiZ9
Why is my Internet connection so slow?
http://windows.microsoft.com/en-US/windows7/Why-is-my-Internet-connection-so-slow
Why can't I connect to the Internet?
http://windows.microsoft.com/en-US/windows7/Why-can-t-I-connect-to-the-Internet
Let us know if it helps!