Don't allow unsafe operations be performed!

I don't know what happens or if you do QA cycles or not but your program has several flaws both UI and semantic/functionality related.

For example you're allowing to create logical partitions in between primary ones in a traditional MS-DOS scheme. Besides having just 4 primary partitions or 3 primary ones and an extended one that holds the logicals, the extended one has occupy the remaining space of the disk. So after a logical partition only logical partitions may be created, failure to do so can lead to disastrous consequences when using a compliant partitioning software.

Another is that it doesn't respect the partition type you choose when creating crazy layouts that shouldn't be allowed. Seriously, in a data critical program such as this one I can't understand the lack of testing this has.

I'm sorry if this seems harsh, but it seems to be bad engineering (I think it's best to say things honestly); if you follow an iterative process I'd recommend making an iteration for just refactoring and sanity/specifications verification and improving software testing. (And/or hiring meticulous, hard working people as well)