In preparations of the coming CPU overhaul of dop, I've anticipated the loss of PATA ports and already acquired a new optical drive and probably the last I'll buy in my life. It's an LG CH10LS28 Blu-ray reader/DVD writer combo. It also has lightscribe support, so I should finally be able to use those discs I've kept lying around for years...
Lightscribe should be possible in Ubuntu per this instruction and playing blu-rays per this one.
While installing this new drive I imagined I might as well remove the old 180GB PATA hard drive that I wasn't using anyway. Since this is all so simple I screwed everything back together without testing and guess what: it didn't boot anymore. Apparently the old drive contained the MBR. Instead of reinstalling the old drive, I thought I might as well fix it properly.
I tried a super grub disk I had lying around, but I had to download a new version (2.00 beta 5). Then I just selected the "Any OS" option and waited for approx 5 minutes but indeed it presented the kernel overview where I selected 3.8.0-22 and it booted properly into my Ubuntu installation.
After that I needed to repair the MBR so it would boot properly without the boot disk, so I followed the "install in Ubuntu" instructions for Boot-Repair. The "recommended repair" setting did the rest.
I don't know how, but after rebooting the BIOS selected the right hard drive to boot from, which I would not have expected since it's /dev/sdb, but I'm not complaining.
Now I just need to remove the 10 second delay in grub, but it's apparently easy to configure.