I actually partitioned my hard drive and set up Ubuntu twice, so now on boot I've got to choose between 2 Ubuntu OS's and Windows. What I'd like to do is delete the Ubuntu partitions and start over. Is that a problem or can I use the GParted utility safely. By the way, there's nothing on Ubuntu at this time that is critical to save
The only problem you will have is that if you delete the wrong partition, you will not be able to boot until you reinstall grub. Grub will be installed automatically if you simply re-install Ubuntu.
As you claim you do not have any reason not to, I would fire up the ubuntu desktop CD, delete the ubuntu partitions, and install into the resulting free space.
If you do not want to re-install, boot the desktop CD, use gparted to delete one of the ubuntu partitions, and then resize the remaining partition to take up the free space. You might need to re-install grub.
Up to you to decide which is easier.
It should not be a problem to remove all your ubuntu partitions and start over with a new install. Just launch the install from CD or whatever you use and remove all the ubuntu partitions when at the partitioning phase of the install. Then just create new partitions for ubuntu as you see fit. Good luck.