Unable to connect to iTunes Store after changing OS

I never had any problem using my iTunes since the first time I use it. But after migrating to Microsoft Windows Vista, I started receiving error on accessing my iTunes.
When I tried to open it, I could not connect to iTunes Store. It keeps giving me an error stating that the network connection timed out. I did not download any software from iTunes store nor change the settings on my firewall that can affect my iTunes.
I am really lost so please help me.
Thank you.
