I managed to get Inkscape Portable with its extension Textext (used to write latex equations directly in Inkscape) to work with MikTex, pstoedit and ghostscript in a fully portable package. No need to add stuff to the PATH as usually required for these apps on Windows.
Here's a link to the full package (zipped) 161MB [old version 0.48]
** Update ** march 2015
Here's an updated link to the full package with the 64 bit version of Inkscape 0.91 (zipped) 233 MB
Note: you can edit the "preamble.tex" file located in the main folder for additional packages and customization to use in the Textext editor.