Physical disk limitations in Windows Server 2003 SP2

I have a server with Windows Server 2003 Standard SP2 with 6 SATA drives and 1 IDE connected on the board and 4 SATA in a RAID array on a card. It only sees 5 drives total. Is there a disk limit in Server 2003 Standard? I can’t find anything online but would like to know before I try to upgrade it to Enterprise.

All the disks are good and if I disconnect some, the others show up. All display in the BIOS so the board sees them.