The IGEL D200 has a standard PC Phoenix Award BIOS - hit the DEL key repeatedly on power-up in order get into the BIOS setup screens. The BIOS boot options are:
There is also a Hard Disk Boot Priority entry that can be set to:
Pressing F9 on power up brings up a boot menu of:
The USB-ZIP entry will only appear if you have a suitably formatted pen drive inserted. If it is doesn't appear then either you don't have a pen drive inserted, or the BIOS doesn't recognise how it has been formatted.
The original ZIP drives were either 100MB or 250MB in size, had a drive geometry of 64 sectors and 32 heads, and had a standard DOS partition table with the drive defined in the fourth entry in the table. It looks like a lot of people take the geometry/fourth entry in the partition table as their target in creating a bootable pen drive when the BIOS won't boot a normal pen drive and only offers USB-ZIP.
As far as I can determine with this BIOS, the only criteria for a pen drive to be recognised as a USB-ZIP drive, is that the pen drive must include a conventional partition table. To see what the BIOS did I took a 1GB pen drive and used fdisk to create a partition table at the start of it. I then created a new partition in the second entry in the table taking the default geometry offered by fdisk (61 sectors and 32 heads). Having used LiLi to write Tiny Core v7.0 onto it, I found it booted without any problems.
In March 2018 I heard from John. His Compact Flash card had gone faulty and so he was booting directly from an external USB disk drive and had had various problems. His email prompted me to check things out. I have a number of SATA SSDs (16GB/32GB/60GB) that I connected in turn to the D200 using a simple USB-to-SATA interface cable. From this check (and John's experience) it looks like the BIOS will not recognise/boot from any external USB drive that is larger than 32GB.
The simple way to check this is to either go into the BIOS to set the boot priority, or to use F9 to bring up the boot menu. In each case, if the attached drive is >32GB, there is no sign of it the list of boot options that you get offered.
Note: If you boot your OS from elsewhere - in my test it was Tiny Core 8.2.1 on a 1GB pen drive - then the drive is detected and becomes available as the OS starts up. It's just you can't boot directly from it.
This drive size limitation is a known feature of several pre 1999 BIOSs. It's odd finding it in a late 2000s BIOS.
As usual I haven't done anything with the native operating system.