If you can merge the contents of your drivers partition onto your main Windows partition and get can confidently remove it you can delete that partition and add extended partitions using its space and the contiguous unused space.
At that point if you want to create an Ubuntu partition as well as create a new Windows driver extended NTFS partition you can.
Having four primary partitions is a dead-end it's best to avoid.
If your computer and Windows can deal with it you may also be able to convert the disk to GPT format--it doesn't differentiate between primary and extended partitions and can have a large number of partitions. Both Windows and your BIOS would have to support that move.
I'm confused by one of your comments. You mention having allocated space for the Windows installer already. If I understand correctly and that's an NTFS partitions on the list never used you could delete it, boot from a DVD or USB Ubuntu installer, and then let the Ubuntu installer handle putting Ubuntu into an extended partition (not a primary one). Ubuntu doesn't generally install on an NTFS partition, using a different file system like Ext4. You don't need to create a partition for the Ubuntu installer itself. You can boot an Ubuntu install DVD and the software on it will do the formatting you need.
Unless you are letting the Ubuntu installer do all the formatting automatically you will have to choose "Custom" for the install type.
In any case you would have to be careful about backing up and having a way to use the backup if there is a problem.