Can't access Google, Wikipedia on multiple browsers?

I am having a weird problem. yesterday Google, Wikipedia and Yahoo worked fine in my PC.. but today all of a sudden i get the

Server not found Firefox can't find the server at www.google.com.

I am not behind any firewall.

I did a malware scan - Still didn't work I checked the host file - Still didn't work I tried in wireless/wired with my laptop - Still didn't work

at last i formatted my PC and reinstalled windows XP but i still get the "Server not found".

Can someone please help me?

Solution 1:

Can you change your Primary and Secondary DNS to OpenDNS servers and check if you can access those sites?

These are the the settings

208.67.222.222
208.67.220.220 

There is a possibility that your ISP's DNS servers have some issues. You should give them a call and double check.

If you don't know how to change you DNS settings click here.