What do you mean by not go on some sites, "Internet Explorer could not display the web page" error etc?

Press the windows logo on keyboard and R simultaneously (Opens run dialog, something Vista/7 do not display by default), this will open a run program dialog box on the bottom left of the screen, type "cmd" without the speechmarks and hit enter.

This will open command prompt black background with white text. Type in here:

Ping google.com

It should come back with reply from then a number (IP address)

If you get stuck let me know as I can remote onto your PC and sort for you if needed?

Far more likely to be browser than connectivity but do the above to confirm first.

Martin