Getting a Windows image onto a flash drive to boot from using an old BIOS

I've got an old laptop (Thinkpad T60, 32 bit, 7 years old) ruing Linux Mint, on which I'd like to install Windows as well. However, I can't get it to boot from the flash drive containing the Windows installation image:

• After writing the Windows installation image to the flash drive (dd if=win.iso of=/dev/sdc bs=1M), it is being displayed as a UDF device. GParted is not able to read any information ("Warning: unrecognised disk label"), but contents can be accessed after mounting. When restarting the computer with the flash drive coected, it is not being recognized as bootable device at all.
• When writing another image to the same flash drive using the same method, booting from it works fine.
• After formatting the flash drive as a single FAT32 partition and copying the Windows image's file contents to it, the device seems to be booted from, but complains about not being bootable ("Please insert a bootable floppy disk"). Doesn't look like GRUB, might be BIOS or Windows.

How could I receive a flash drive with the Windows image written to it, from which my (maybe old?) BIOS is able to boot?