You can download Bootice from here.
1)Now insert your pendrive you want to resize on your running computer.
3)Select your pendrive which has to be resized and select the option Parts Manage.
4)Your pendrive is selected and then select the option Reformat USB disk.
5)Select the option USB-HDD mode(Single Partition) and click on next.
6)You can change the file system of your pendrive.Its better to delect NTFS file system.You can label your pendrive also.And then click on OK button.
7)Click on OK button.