WD Elements problem!!

Hello, I bought a WD Elements 1T, and its seems working good on my mac system, i use for time machine program on mac system, but when i change to windows system, when i connect to computer the blue light on the drive came out as usual, but does not show up in my computer. Do not know how to fix this problem

before I am use windows XP and now I am using windows 7 RC both can not work..

Hope someone can help me about this.. and also I try to reformat or format i cant because i cant find the drive...