WD4003FZEX only shows 1677.90 GB instead of 4 TB

Upgraded RST, but now Windows Disk Management sees two partitions, one 2048GB and the other the remainder. Options for deleting the volume first partition are greyed out, as are options for converting the whole thing to GPT, etc. So something is still not compatible. Is it possible that the SATA controller hardware is too old regardless of the driver? It’s part of the motherboard chipset, but I haven’t had any luck yet figuring out the model number. Thanks!