Application to check website availability around the world

Hello everyone,
I am on Windows XP, and looking for an application that could be used to check my website availability from cities / countries around the world.

Many times it happens that for some reason my website is unavailable from some cities of India, or Russia, or for example isn't available via some internet providers in my own country.

So i thought there could be some sort of professional program like that, that could be flexible used to verify website availability from different cities / countries / internet services providers.

Any good suggestions around?

Big thank you in advance.
Regards,

You mean accessible, not available. I don't know of any such app.

What i want its something like these online services:
h t t p : / / w w w . uptrends . com/aspx/free-website-server-network-monitoring-tool.aspx
h t t p : / / w w w . site24x7 . com/check-website-availability.html

Only that i want a bit more sophisticated application that could be installed on my machine, instead of an online service subscription.

http://gomez.com

It's a service you can utilize to set various points of presence around the world to check the status of your site and alert you when it falls below a customizable threshold.

Nice one! Thank you!