Large (4tb) drive not seen by Windows, smaller ones ok

I know this is supposed to be a Windows 7 forum, but my problem is on a Windows XP machine. A lot of you experts learned your stuff on XP so probably have a good idea what the problem might be.

I have an HP XW4100 computer that I use to store backups. It doesn't have to be fast, and XP has worked well on that machine.

It has IDE and SATA ports on the motherboard, and I have added 2 x 4TB Seagate HDs connected to the on-board SATA ports. Using Seagate DiscWizard, I am able to split those drives into a 2tb and 1.6tb drive each so XP can partition and format them with MBR. So far so good.

Wanted to add some more 4TB drives, but there's no more SATA ports on the motherboard. Bought a Vantec PCI SATA card which uses the SiL 3114 chip and has 4 internal SATA ports. Installed the drivers, and when pluggin in an older 500g WD SATA drive, the OS sees it, I can partition it and use the drive.

When I plug a Seagate 4TB drive into that controller (even one that works with the MB SATA port), I can see the drive in device manager, Seagate DiscWizard can see the drive and partition it, but the drive will not show up in Disc Management so I can't use it.

I would conclude from this that the SiL 3114 chip has issues with large hard drives, while the Chipset on my HP has no problems. Strange though that the drive shows up in Device Manager and DiscWizard. Seems like a driver issue, but I've tried all the SiL drivers, and as I say, a smaller older SATA drive works fine.
I also tried using the jumper on the Seagate 4TB drive to slow it down to SATA 1 speed, but that made no difference.

So, I guess I'm wondering if anyone has ever run into this problem before? I can't find any information at all about there being problems with the SiL 3114 chip and large hard drives, or SiL driver issues.

Will I have this same problem if I get a different PCI SATA card with a different chipset? Has anyone tried this and found a chipset that works properly with large hard drives in XP?

Really not interested in going to Win7 on this machine either.

Have you tried partitioning your HD so that your partitions are < 2tb?

From my understanding XP doesn't support > 2tb drives.