i think XP permissions default to somethign screwy for the hard drive check to make sure you have rights on the hard drive as the user you are using when you get this error. also check out this link maybe it will help:
http://digital.ni.com/public.nsf/3efedde4322fef19862567740067f3cc/862567530005f09c862565370000ba98?OpenDocument
good luck
Dan