Joomla 1.5 Installation fails because of missing file

[mahagr]

JInstaller::install: File 'tmp/install_4e994559c855d/admin/handout.config.php' does not exist.

[mahagr]

If you add the missing file, you get this (FTP mode on):

Component Install: Custom install routine failure
Unwriteable: /
Installation failed! Click here to uninstall Handout. Make the folders listed above writable and try again.

[mahagr]

Uninstalling component as asked above:

    JFolder::files: Path does not point to a valid folder or the folder has been deleted.
    JInstaller::install: ERRORXMLSETUP
    JFolder::delete: Path does not point to a valid folder or the folder has been deleted.
    JFolder::delete: Path does not point to a valid folder or the folder has been deleted.
    If this Extension has created tables or installed additional files, they must be removed manually.