Cannot open few websites

Hello ppl,

I'm not able to open or download from few websites like microsoft(the site opens, but whenever it comes to download firefox returns" connection was reset, unable to open"), zone alarm(same problem), remime home page(birthday reminder), & few other web sites.
I'm using bsnl broadband. Even when i disable all firewalls(including windows firewall), i'm not able to open few sites. Changing the web browser even doesn help.
This has been a problem for years,,, i'v formatted C drive many times over these times but the same error continues.. Kindly help. I'll be grateful.