I have been having trouble reinstalling GRASS on XP.
I have downloaded the stand-alone, and via OsGeo4W, and installed,
reinstalled, removed, rebooted, reinstalled, etc., in various different
sequences without success.
QGIS also isn't working.
When GRASS starts, the black console window comes up,
Hi,
it seems that the installation failed since QGIS is not working too. It
might be better to ask about this on osgeo4w-dev mailing list.
You can also try standalone GRASS installer but it is based on OSGeo4W
anyway.
About Windows XP, I'm not sure if you are doing the right think in using
it.