MacBook – Disk Utility won’t allow me to delete and resize partitions

There might be a misconception somewhere in what you say. You can run Disk Utility from the original system disc WITHOUT re-installing OS X.

I ran into a similar problem recently, on which running Disk Utility from any of the existing partitions would not work. I then tried running Disk Utility from a restore disk I had copied to an external USB-drive and to my surprise it was not successful either. Ultimately, the only way I was able to get Disk Utility to re-partition my drive was when I executed it from the original system CD that shipped with my Mac.

Again, you can launch Disk Utility from the setup start up screen by selecting it from one of the menus. You do not require to re-install OS X. Hope this helps.

iPartition

For all my partitioning, I use and recommend iPartition. It will allow you to resize partitions without deleting any data. It also works for Boot Camp volumes and other PC disks. It will automatically move partitions if necessary to allow resizing into free space that is located before the partition.

With iPartition, resizing a partition is as simple as selecting it, grabbing the resize handle and dragging. Not only that, but if you have several operations to perform, iPartition lets you queue them up and run them one after another, so you can have a cup of coffee while iPartition works. This feature, coupled with iPartition’s ability to automatically rearrange your existing partitions when necessary, makes iPartition the easiest partitioning tool that you’ll ever use.