You can only have up to 4 primary partitions per disk ( or mixture of extended/primary)
Your issue is that you have all of those allocated. What is in each partition ?
Did you partition that drive for data storage prior ? If so you need to consolidate to open up a partition for Linux.
If you are not sure what is on the partitions please do the following and post.
First mount the drives then post the output
df -hTl --total
I would like to see the files systems by partition so we can determine which is windows.
Filesystem Type Size Used Avail Use% Mounted on
/dev/sda1 ext4 53G 13G 38G 25% /
tmpfs tmpfs 5.0M 4.0K 5.0M 1% /lib/init/rw
tmpfs tmpfs 397M 708K 396M 1% /run
udev tmpfs 1.9G 0 1.9G 0% /dev
tmpfs tmpfs 793M 2.0M 791M 1% /run/shm
/dev/sdb1 ext4 917G 547G 324G 63% /media/N-Space
/dev/sdd1 ext4 1.4T 946G 360G 73% /media/E-Space
/dev/sdc1 ext4 294G 191M 291G 1% /media/Turtle
total - 2.6T 1.5T 1015G 60%