No easy way...but
Overall it will likely be far easier to re-apply all your customizations and configurations to a new install than to delete all the existing data. Great exercise to force yourself to work in such a way in the future also where all these things are developed on a test system, then implemented in production, and managed in source control.
- File Customizations (e.g. new states, roles, data types, etc.) can all be applied quickly and easily to a new install.
- Many but not all configurations (OIRs, LC's, WF's, QB reports, etc.) can be exported and saved as files, then imported to a new install.
One other thought: It may be possible and desirable instead if you really want to continue using the existing install to create a new Organization and newly load all your data to that new Organzation, abandoning the existing one by making it read-only to admin and non-accessable to all regular users. How this would work is greatly dependent on what configurations you've made at Site level and which at Org level.
