[ALUG] gparted

Hullo there. I have a computer currently dual-booted with a windows partition and a debian one. I want to use a small amount of disk space to install ubuntu to have a look at it. If I run gparted to try and shrink the current partitions, the resize option is not available. Is this because I didn't use LVM to create the original partitions? Is there any other tool I can use to resize? Thanks, Jenny