I'm guessing that Win10 only sees the camera's CF card as an external storage device but not the camera itself when connected to your PC with a USB cable. The short answer is that windows, and probably Canon for that matter, have no logical reason for continuously upgrading their software so that a nearly 20 year old camera is recognized on a more widely used modern operating system. I suspect they're kept busy enough keeping all the newer camera equipment compatible. I ran into the same problem several year ago with a used Rebel 300D when I was was running Win7.
If you had the Rebel XT's original Canon Utilities Disk you might, or might not, be able to even install it on win10. At least not without having to jump thru a lot of hoops and then really not seeing much of a return for your efforts. It might not easily install on anything newer than Win XP.
If your main concern is downloading images from the camera to a PC you should still be able to do so using Windows File Explorer via a USB cable connecting the two. Make sure you have a well charged battery in the camera when doing so. But the more elegant solution would be to get an external USB CF card reader and not have to depend on the camera's battery.
If you go the card reader route, a note of caution is suggested. The CF card's contact pins in the camera and the card reader can be a bit fragile. They won't tolerate a lot of "horsing around" when installing the CF card in either the camera or the card reader. Install the card in the correct orientation slowly and deliberately before fully seating it in either device and you'll have no problems.
