The Thinkpad T23 feels like a classic laptop. I spent too long trying to install an OS, though.
So here's a tip that'll save you time. In the BIOS enter the boot menu and press CTRL + ENTER on entries that are marked with a + symbol. This will expand the specific list to show the USBs that are attached. USB disks will appear under "Hard drives" and not "Removable disks". Make sure the USB disk has a higher boot priority than the main disk.
Since it's USB 1.1 the speed will be extremely slow when loading the installer. However, I noticed that the USB works fast enough for a Wi-Fi adapter.