Double Commander
Open Source - http://doublecmd.sourceforge.net/
2xExplorer
A great, free, enhanced Windows Explorer replacement - the name is terrible for search engines though, so here's some search engine fodder: 2explorer. The newest vesion is called xplorer2. - http://netez.com/2xExplorer/
ExplorerXP
Free for non-commercial use. It has tabs! Nonags.com rated.
Note: I've had issues with ExplorerXP. For some reason, it disables multimedia keys. Also, it stalls on some things. Today, it stalled when I had a blank DVDRW in the drive. - http://www.explorerxp.com/
Explorer++
Open source - has git repo.
https://explorerplusplus.com/
tags: explorer, xp, explorerxp, alternative,