Windows XP support was officially dropped with this issue: http://forge.typo3.org/issues/11683.
Even if you make the symlink() PHP command working on your Windows XP, e.g. with third-party libraries, FLOW won't work because the Windows version check is integrated in the bootstrap:
I would suggest using a Vagrant box with a Linux VM. Thomas Layh prepared a Vagrant box with TYPO3 Flow which can be found on https://github.com/tlayh/vagrant-typo3flow.
A manual is included in the Readme. What the readme doesn't say is that you first need to install VirtualBox for Windows (to be found on https://www.virtualbox.org/wiki/Downloads). You also have to run "vagrant plugin install vagrant-librarian-chef" after step 2 and skip step 3 on Windows.