partitioning - Add unallocated space to extended partitions

In a PC where I need to install Ubuntu, I have the following disk partitions from the left side of partition table as of now:

1. NTFS - Primary windows vista


2. Extended - 3 Nos. all NTFS - middle one contains data


3. Unallocated space


4. NTFS - Primary


5. NTFS - Primary HP Recovery

My intention is to add unallocated space to the extended partition. Will I be able to use Gparted to do it?

Also, can I install Ubuntu in one of the extended partitions and make this unallocated partition the home partition for Ubuntu. I am not able to add new partition in this unallocated space as disk manager in vista throws up an error no free disk space to complete the operation. I read in some forum that OEM installations allow only 3 primary partitions and one extended or 4 primary ones. Is it true for OEM's only or its a universal rule?

Yes, you can easily add the unallocated space to the extended partition with GParted. Just select the extended partition (not one of the logical partitions inside it) and then choose the resize action.

You can not create a new primary partition from it; max. 4 primary or 3 primary + 1 extended partitions are allowed in the old MS-DOS (also incorrectly known as "MBR") partitioning scheme. So this has nothing to do with Windows OEM installations or whatever.