Thanks for the advice Mitchel. I finally got DNN4 to install. found it was a problem of  file permission afterall. However another odd problem surfaces (sigh) :
I logged into  admin and made some changes basically in the site configuration (name, keywords etc), added a user, and logged  out. Now I try to login to Admin again and the login page does not open at all. I only get the home page. I guess I probably touched something I shouldn't have in admin ( though I have no idea what).
I tried to do the most logical thing in such a situation (as far as I think) : I first attempted to drop the database so that I could reinstall. But the database would  not be deleted . I get a message that it is in use (it is not).
I finally deleted it and added a ned database and then this error comes up :

Error

Could not find stored procedure 'dbo.AddEventLog'.

Can you tell what I have been variously doing wrong ?
Thanks

Thanks Mitchel;
I solved this by rebooting the machine, and then dropping and recreating the database. I checked permission for the database and files and then recompiled the .sln file . Installed again thanks. (I am becoming an expert at this he! he!).
Now for the fun part :
1.I  am working on an office server . How may guests view work progress from over the internet ? I am presently accessing the work on http://localhost/mysite
2. How do I finally move my website to a remote host after I have finished work on it . I can FTP the files but the database is still local isn't it ? how do I  also safely move the database without destroying everything ?
Thanks