The good news is that you can replace the IDE disk with a SATA disk or SSD. The bad news; neither is likely to fit in the T30 case.
It has occurred to me that your notebook is not the original hardware for the following reasons:
SCO 5.0.5 was superseded by 5.0.6 prior to 1999, and 5.0.5 does not reliably run on pentium 4 systems.
https://www.unix.com/303018403-post5.html
You can switch to a SATA drive, as long as the motherboard bios supports the drive in legacy mode (emulating an iDE controller.)