Distro hopping may sometimes lead to borked bootloaders and/or installs. Grub/Lilo are usually relatively easy to google around for a fix but fixing a borked windows install wasn’t as easy to find a fix. Borked mine so I’m posting this over here so I can use it for later reference.
Boot from the Windows 8 install CD and navigate to the command prompt. I somehow managed to disable the “active” (bootable?) option for the partition Windows was installed so “bootrec /fixmbr” and “bootrec /fixboot” weren’t working.
diskpart list volume # Select the volume where Windows is installed: select volume X active
This activates and turns the partition bootable.
At this point “bootrec /fixmbr” and “bootrec /fixboot” were reporting success but the computer still failed to boot, something about a damaged BCD. “bootrec /rebuildbcd” did the trick.