Someone on the KiCad mailing list has created a windows installer of the BZR5025 code base, including libraries, demo projects, docs…
I’ve mirrored it on my server for your convenience.
Please note that this version uses library-tables and the new ‘pretty’ footprint format. It also uses the new “version 4” board format, which is not backward compatible. Boards saved with this version cannot be opened with older KiCad releases before BZR4958.
Please take the usual precautions when working on boards that are dear to you – make backups and use a decent version control software (git comes to mind), so you can easily roll-back if something goes wrong. Commit frequently!
You may want to look into using a virtual machine (VirtualBox, VMware…) for testing these releases.