Installing Linux without any removable drive
I dont know if this is common practice or really new, but it just occurred to me out of pure necessity (the box in question can’t boot from USB, and i have no empty CDs, and only broken floppys).
You can install Linux (tested for the debian installer, I think it should work for the most other distros too, but this is untested) without any boot media.
You just remove the HDD from the system in question, put it in any other box with a working OS, run unetbootin, slap a netinst bootdisk of your distro of choice on the disk*, put it back in the system you want to install linux on, and voila – the installer runs just fine. The trick is that the debian installer seems to put all needed files onto a ramdisk, so there is no problem in formatting the disk it originally booted from (of course it works only with netinst-images).
As I said before, this may not be entirely new, but it just saved my ass – I had already been screwing around with floppy disks 
This can be particularily helpful if you have an old laptop with a broken optical drive. If the HDD is PATA, you will probably need an adapter to write on it, but these things are readily available for small bucks.
I hope this blog post helps someone in a similar situation someday!
*unetinst seems to be a bit picky about the disks it accepts. If you can’t select the disk in question, just run it over any other spare disk (an usb flash drive comes to mind) and simply copy all of the generated files to your disk.