Can't open US sites

hi,friends i have this strange problem.When conncet internet and if i open any indian sites like airtel.in ,yahoo.co.in etc it opens immediately in my pc,but whenever i try to open US based sites like microsoft.com/yahoo.com they are not opening is this problem with Internet Service Provider or my pc.
Please help.

Hey i was also facing same problem in opening some sites with Internet explorer.but then i try to open these sites using different browsers like Mozilla firefox,Opera,Google chrome etc and my problem got solved.

Maybe because some of the OS add the US web sites to the blocked list, so the IE can't open the US web sites.