v2.1.3 is the last version officially supported in XP. However, v2.2.2 is the last version known to work in XP :-)

Note: Version 2.0.6 of Audacity is the final version for XP lacking Service Pack 3 (32-bit systems) or Service Pack 2 (64-bit systems).
Also use v2.0.6 if your hardware does not support SSE 2.

Good to know: WASAPI is not available on Windows XP.