All Content Lost

i’ve been running wp 1.5.1 for about 5 months now, and everything’s been great. today somehow when my friend tried to access my blog, my site was missing and he received a message saying that wordpress was not set up and asked if he wanted to install it. he thought he had to create a login to see my site, so he put in his name and email address and all that. this created a new account that somehow overwrote my old account. all my posts are gone. the only things that are not lost are the themes and plugins i installed. but all the original wordpress content seems to have been reset.

if anyone could help me figure out how this happened and how i can restore my old content, it would be much appreciated. i have ftp access to the server, but no access to the mysqp database, though i can find someone who can get in there if its required. thanks for any help you can give.