WP says ‘already installed’

Hello,

Yesterday I made a mistake with WordPress, and wanted to reinstall it.
Here’s what i did wrong;
– I wanted to change the url, so that my http://www.mysite.com wouldn’t get the “/wordpress” tag. In options, i changed the “wordpress” and “weblog” url, but ever since then everything went beserk.

Here’s the problem;
– As soon as I hit “save”, WordPress didn’t load the CSS anymore, and I couldn’t log in.
– I though oh well, I didn’t do anything importing yet, so I’ll just delete the wordpress-directory, and reinstall it.
– But i can’t install it on my webspace anymore. It keeps telling me that I already installed wordpress, even though I deleted everything. I even asked the hostingcompany to reset my webspace.

Could someone please help me out? I downloaded a clean WordPress (instead of using the tinkered version i already had), but nothing seems to work. If I upload a new and clean version of WordPress, I can still see the posts and images that I deleted (I completely olbiterated them, so there’s no way that these images can exist).

Thanks in advance,
Joram