Please do a full dump of the second unit's HDD; most of the units come with different test cases installed, it would be great if we could collect them. R&S states (though that's debatable) that they no longer _have_ the firmware for these things on their servers. Also the HDDs keep dying. Make a backup.
In one of my units, I replaced the HDD with a PATA-to-SD bridge and a 64GB SD card, and it works fine.
USB is slow since it's 1.1 only. The best way is to get into Windows, use Network and copy over the 4.34 firmware (if you want that) on the DOS OPSW drive (\CMU\BIN_V4.34); copy that to the target device. Then enter the version manager (boot into DOS OPSW, and when it beeps three times, press menu/select. Select the software version and update to it; it will reflash everything to the right version).
Keep in mind that in order to use the Windows software, you need to be on V3.23 (or V4.00 which I haven't seen). But you can easily flash back-and-forth (you can have multiple version installed and use the version manager to activate the correct one).