GarageBand is exclusive to Apple Mac and iOS platforms and is not available for Windows PC. GarageBand is free to download from the iTunes App Store and comes pre-installed on Apple Mac desktop and laptop computers.
A free Windows alternative to GarageBand is LMMS. LMMS features a mixing interface with built-in virtual instruments, effects and loops that users can assemble and export as full songs. LMMS supports MIDI import, FL Studio project files and Hydrogen project files.
Stagelight is a Windows application that features a multi-track editor, drum machine, effects and support for third-party plugins. Stagelight is compatible with instruments such as keyboards, synthesizers, and electronic drum kits through the MIDI interface.