Here is some "good enough" software I've found for Windows:
- To diff directories, e.g. sync music or photos: FreeFileSync 6.3
- To diff the content of files, e.g. source code: WinMerge
- Windows Explorer alternative: xplorer 2
- To encode mp3s: LAME
- To see where your disk space is being used: Treesize
- To remove spyware: Spybot: Search & Destroy
- Torrents: qBittorrent
- N64 emulator: project64
- Programmer's text editor: Notepad++
- ebook management: Calibre
- Manage iPhone music outside iTunes: Media Monkey
- Graphics maniplation: GIMP
- Rename files: Bulk Rename Utility
- Macro recorder: Autohotkey
- Media player: VLC, or MPC-HC (not tried)
- Music player: Winamp
- Documents and spreadsheets: Microsoft Office
- (LibreOffice and OpenOffice are NOT good enough)