partitions too big for windows 7?

So I have a 3TB external HDD. Connected through USB.
It was preformatted to one volume of size 3TB, but I wanted to split it into 2 volumes of 1.5TB each.
I first used 'shrink volume' to shrink the pre-formatted volume to 1.5TB... so far so good. But when I went back to 'New volume' the other 1.5TB, I found there were 2 un-allocated spaces of ~700GB each.
Next I tried to 'New Volume' one of them and 'Expand' it to grab the other 700GB and make one volume of 1.4TB, but no dice. After I got the first 'new volume' to work, there was no way to expand it (greyed out).
Worse, now I have 1 volume of 1.5TB, and 1 volume of 700GB, and 700GB un-allocated... but it won't let me 'New volume' the last un-allocated part.

Now what should I do? Any (helpful) suggestions? Did Windows somehow force that second 1.5TB to be split up to 2 700GB parts? Is there a way to join them again?

Thanks much!

Hey, have a read of this Support for Disk Drives Beyond 2.2 TeraBytes (TB) and 4K Advanced Format Sectors
you may need to find the version applicable to your model Seagate/western digital.

There are certain tools/drivers you may need to properly format a 2.2tb + hard drive if you don't have a UEFI bios motherboard. Also a 3tb hard drive will need to have multiple partitions if it has a MBR based partition as opposed to a GPT partition as explained in that link ^

So my suggestion would be to download the applicable tool to your computer and use it to format your drive into GPT partition and a mixture of partitions as you want

Also. you cannot use it for a boot drive unless you have a UEFI bios. ( just for reference )

Try Partition Wizard Create Partition - Video Help.

Make sure you have the latest BIOS update for PC which may deal with larger drives.

I'd use 3 different partitions on the drive.