There are half a dozen questions here why the iPad doesn't charge (or displays this at least) on most Windows machines. I have one more to add.
Of course my iPad (1st gen) does charge on my MacBook (late 2008) under Mac OS X. However, when I boot Win 7 in Boot Camp, it says "not charging".
As I see, the logic board is capable to deliver sufficient power. Why does this change under Windows? And what could I do about this, since I do need to use Windows sometimes and I'd like to charge my post-PC device then.