Are you intending to use the 4TB hard drive as a Boot Disk or a Data Disk?

What Operating System will you be using with this 4TB hard drive?

Use the following guideline when using internal hard drives with a capacity of 2.2TB and above:

Windows XP (32-bit)
Can be used as a Boot Disk? No.
Can be used as a Data Disk? No.

Windows Vista SP1 or later (32-bit)
Can be used as a Boot Disk? No.
Can be used as a Data Disk? Yes.

Windows Vista SP1 or later (64-bit)
Can be used as a Boot Disk? Yes, with UEFI BIOS.
Can be used as a Data Disk? Yes.

Your P5KPL-AM motherboard's BIOS is not a UEFI BIOS.

A graphics card with 2GB of Video Memory should have no problems running on the P5KPL-AM. The Intel G31 Express chipset on that motherboard only supports PCI Express Base Specification, Revision 1.1 so if you use a PCI Express 2.0 or 2.1 graphics card you won't be able to benefit from PCI Express 2.x's doubled per lane throughput.