I've done it by myself. I removed ubuntu partition then put the ubuntu CD and and boot my PC from there. So now I've reinstalled (not uninstalled) ubuntu and everything work perfectly.
Edited for Simon Sheehan :
I've inserted the Ubuntu CD for installing ubuntu (I've downloaded the ubuntu from their official site and bur it to CD). Then if the computer doesn't boot your CD u have to enter the BIOS and set the booting order - put CD-ROM on first place. Then restart and your computer should boot ubuntu installing.
When on windows click right mouse button and enter manage->disk management then find the ubuntu partition (usually this is a partition about 10GB (the size that you have allocated in the beginning ) ans with no letter (like C,D)) then right click and delete. Then If you want to use that partition on windows right click and click Make new logical drive (I'm not sure because now I'm not using Windows). Hope the you received your answers.