Maybe your DNS resolution is not working.
Try browsing using IP addresses, not names, to see if it works.
Enter 188.8.131.52 in your browser, and see if you can browse. (thats Google's website IP)
If it works, we can work from there
Given your comments, I have a strong suspition this is your ISP's fault: when you use IP addresses, it all works fast. When using names (meaning a DNS query is triggered), it works but it is very slow. This indicates your config is fine, but there is a problem @ your ISP.
My suggestion is: try to contact them, and ask if they are aware of any DNS problemns. Maybe they are doing some maintance in their servers. Also, ask about the IP numbers of their DNS servers. Then, use
Start Menu -> run -> cmd -> ipconfig and compare if the currently assigned IP for DNS servers matches the ones your ISP provided you.
IP (numeric) addresses wil always be faster than using (textual) names like www.google.com. Thats because when using names it must translate the name into an IP address. Your machine query another computer (a DNS server) that has a table matching every name to its IP address. So how fast it is done depends on how fast/busy the DNS server is (and how good/crowed is the network traffic between you and the server)
So using public DNS servers, like you probably did when you searched solutions in the net, is not a good idea: they are usually very busy servers, and they might be "distant" (network-wise) to you. Distant server means high latency, slower response, leading to slow access.
The best solution is to make sure you're using the DNS servers your ISP provide you. Since its your ISP server, you have the fastest possible connection to it, and they are usually not so crowded like public DNS servers.
(small note: your machine (the OS / browser, actually) keeps a small record (a cache) of "recently queried" DNS names, so it only needs to translate www.google.com once. Subsequent browsing/pinging to same address will be (almost) as fast as using the IP address, because theres no need to query the DNS server again. The OS / browser just look at the internal DNS cache)
Hope that helps, and feel free to add more input if you need further help!