You provided with us too small info about an issue. PLease, send more details. Does installation script opened in your browser? On what step of installation do you have troubles?
If you database is 0MB then you have lost your database!
Check to see if you have ANY tables!
Restore the database from your latest backup.
If you have lost your database get onto your host fast and see if they can restore your site form a backup they may have taken!