Welcome aboard elite, are you sure it's your web site and not your local computer and or Internet connection? It's highly unlikely that anything someone did to your computer could destroy the online web site unless you were hosting it from the office.

Have you tried contacting your web site host, explaining the problem and with full details of ownership of the site and of your hosting account ?
Maybe they will give you further instructions.

:: peering into crystal ball ::

Before your computer crashed, it contained

#1 a highly visible alias to the FTP or equivalent for your site
#2 a password file containing the site-access password so nobody had to remember it
#3 your offline backups of the site pages
#4 (et cetera-- I've just tossed in the most likely guesses)

Let's assume for the sake of discussion that you were not hosting your own little server from your office computer. People don't do that unless they are Serious Computer Geeks, and your post doesn't come across that way ;)

Can you still get to the site in your browser, like any outside visitor? If so, the site is not lost. What you've lost is its backup files (maybe) and/or a painless way to access the real (online) files.

For starters, round up the person who set up the site for you in the first place. They will know what's missing and how to restore it.

welcome to WebmasterWorld, elite street!

we have lost access to our website

what type of access have you tried?
can you GET your home page using a web browser?

I am assuming the OP means "lost FTP access to the site and cannot edit or change it now".

The hosts should be able to reset the FTP access password on production of suitable ID.