A system of that vintage will be limited mostly by the bios. It will not likely see all of the space currently available on any IDE drives available today without multiple partitions. Even then it would be a pita at best.
The single best workaround would be to use a IDE controller card, provided you have an available PCI slot.
Because the card uses it's own bios and addresses 48 bit lba,you avoid the 137GB limit.
I use to use the promise line of cards in the win95\98 days on older systems. They worked well. Example here.
As for your usb port, it likely only supports the older\slower 1.0. You would want to make sure any usb device you use is backward compatable. Once again, you may find an upgrade card for that too but you don't want to push your PS too far.