I do not provide binaries for Windows XP any more (I ceased building for XP one year and a half ago due to the move LL did to VS2013 and the fact they don't provide VS2010-compatible updated pre-built libraries any more).
You can still, for now, build yourself a 32 bits, Windows XP compatible binary from the source of the stable branch (v1.26.20). You will find the instructions in the linden/doc/WindowsBuildHowto.txt file of the sources tree (see also
this thread).
However, and like I announced in the
roadmap, v1.26.20 will be the last branch to allow such builds, and starting with v1.26.21 you cannot any more build the viewer for Windows XP (neither for Vista).
Windows XP is deprecated, riddled with security holes that Micro$oft won't plug any more, and provides a poor stability as an OS. Windows XP is dead, forget it (simply upgrade to Windows 7: it will run better than XP, even on old machines).