Successfully installed Phing 2.3.0beta1 using PEAR on a Windows XP machine:
C:\Programs\xampplite\php>pear install phing/phing
Did not download optional dependencies: pear/VersionControl_SVN, pear/PHPUnit2, pear/PhpDocumentor, pear/Xdebug, pear/PEAR_PackageFileManager, use --alldeps to download automatically
phing/phing can optionally use package "pear/VersionControl_SVN" (version >= 0.3.0alpha1)
phing/phing can optionally use package "pear/PHPUnit2" (version >= 2.3.0)
phing/phing can optionally use package "pear/PhpDocumentor" (version >= 1.3.0RC3)
phing/phing can optionally use package "pear/Xdebug" (version >= 2.0.0beta2)
phing/phing can optionally use package "pear/PEAR_PackageFileManager" (version >= 1.5.2)
downloading phing-2.3.0beta1.tgz ...
Starting to download phing-2.3.0beta1.tgz (397,990 bytes)
.............................................done: 397,990 bytes
install ok: channel://pear.phing.info/phing-2.3.0beta1
However, the script C:\Programs\xampplite\php\phing\phing.bat refers to the file C:\Programs\xampplite\php\pear\phing.php, but that file doesn't exist.