Windows 7 has way too much free space, is it possible to get 100GB from Windows7 and give it to Ubuntu? Thank you.
Using gparted you can first shrink your Windows partition and then expand the Ubuntu one to claim the unused space.
Apologies for using caps, but it's important. Back up your data.
Download EASEUS Partition Manager, it is free, just be careful that you do not destroy your windows partition, resize the partition to a second one for 100GB, then apply and it will allocate that much from your already existing partition without destroying windows. Then you can install Ubuntu on the new partition you created.