When installing Simple-Press using the WordPress installer and it fails with the message PCLZIP_ERR_BAD_FORMAT in most cases this is caused from not having enough disk space on your server.
If you receive this error then you should first check the available disk space on your server. Due to the numerous different types of servers we can’t say how you would check yours, but most hosting companies provide a way you can determine your available disk space.
If you are sure there is enough disk space there are also quite a few discussions on the WordPress Support site regarding this error with other plugins that may help you narrow down the issue.
We recommend at least 50MB available for Simple:Press, it’s theme’s, plugins and the additional database entries. Your installation may require quite a bit less once installed but there does need to be enough space for both the Zip file you upload and for it to be expanded before the Zip file is deleted.