actually you should only have 3 primary (or"normal") and one extended partition, in that extended you can create several more partitions.
actually i think you can't create more than 4 primary or 3 primary and one extended.
so say you make the new a replacement for one of the present ones and resize it to give enough room then you can create remaining partitions INSIDE that, the extended partitions CANOT be used it is merely a virtuall partition to help dviding the disk further.
ask and i wil try to help (tired, have to sleep, sorry)