External Hard Drive Problem

Hello,
My laptop DELL inspirons 1420

i bought a external hard drive (500GB )[CAN SUPPORT ALL WINDOWS and MAC} .. my house have 3 Operating system (Windows XP , WIndows Vista and MAC OS)

IN MAC OS PROBLEM
the external hard drive can support in MAC OS , JUST CAN see and partition ...CANNOT EDIT ,copy paste ... ?? any help for this

IN Windows XP PROBLEM
my external hard drive completely cannot support , right down corner .. it show hav installing ... ... my computer cannot show it ... ANY HELP

IN Windows Vista and 7
ALL THINGS OK

PLSS FIX
Thanks in advance