Thanks for testing, emufan.
Due to license issues, floppy support (provided by AROS sources) is not enabled in the official binaries. If you want to use it, you have to rebuild EmuTOS yourself using "make amiga AROS=1". You will be allowed to use the resulting ROM, but not to redistribute it. I expect those license issues to be fixed in next release, as soon as I get Toni Wilen's agreement to reuse his code in GPL software.
For IDE disk emulation, you need to associate a harddrive/hardfile to the IDE0 channel.
1) WinUAE "harddrive". Any drive with a FAT16 partition is OK: USB flash drive, CompactFlash, SD-Card... Beware, WinUAE does not lock FAT16 partitions when it accesses them, so if you wrote data in EmuTOS, be sure to unmount the drive from Windows after closing WinUAE, to avoid data corruption. After that, you can mount the drive again and use it as usual.
2) WinUAE "hardfile". You need an image of a full disk, or a single FAT16 partition. With Linux tools, you can create a blank FAT16 image using "mkdosfs" or "mformat". In the hardfile settings, you need to click "Enable RDB mode" otherwise it will not work.
Beware, hardfile seems to have big trouble with the last WinUAE 2.6 betas, use the latest stable release instead.
After that, EmuTOS will detect the C: drive in the welcome screen, then a C: icon will appear on the desktop. Both read and write will work.