I can think of few things:- A common option in the BIOS is something like "Legacy USB Support". This translates a USB mouse and keyboard into PS/2 equivalents at the BIOS level. While I don't like this as a long term option, using it to get OS/2 installed seems reasonable.
- Are you sure it is USB1.1 and not USB2? Which Dell Optiplex is it? A quick look at the Dell site shows the models only have USB2. I assume older models had a mix, so, you need to be sure what you have.
- The USB1.1 drivers are USBUHCD.SYS and USBOHCD.SYS. USBEHCD.SYS is for USB2. As you managed to get this loaded, it sounds like there is a USB2 controller. To be sure, you need to get OS/2 loaded, and run hcimonit.exe to detect and display the controllers.
- Looking at my config.sys, the USBUHCD.SYS statement is the first of the USB statements, followed by USBD.SYS. But, the USBBASIC readme says what you have is OK without the /REQ parameter.
- What version of the USB support are you using? At least one version required a newer kernel or loader. It's possible you will need to put these on the diskette as well. Sorry, but, I don't remember the details of versions needed.
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David