Firsty do you have the latest driver for your card, http://www.ni.com/support/gpib/versions.htm.
Kindly refer, http://digital.ni.com/public.nsf/3efedde4322fef19862567740067f3cc/5abe7a450c07ffdd86256ac000668ea1?OpenDocument (XP was built over W2k so this will apply to XP too). For security a non-administrator cannot change the GPIB Configuration (unless a power user), one can use ibconfig though.