first I had only windows 7 installed then I installed ubuntu 11.04 and gave it alot of space now I want to take free 140GB which on the ubuntu partition and give it to the windows partition how can I do that?
Using a live cd of Ubuntu (or any other distribution, most probably) you can use gparted (sometimes called "gnome partition editor", found in the system/administration menu of the classic desktop) to resize the ubuntu partition to something smaller and then resize the windows partition to take up the space you just freed.
(By the way, you can't use gparted from inside ubuntu because you want to resize the partition you are currently using. That's why i proposed the live cd. You can also use gparted's own live cd , if you don't have an ubuntu one. It can be found here http://gparted.sourceforge.net/download.php)
You can find more info on gparted's documentation (here, for example http://gparted.sourceforge.net/larry/resize/resizing.htm) but the whole thing is pretty self-explaining once you are in front of gparted.