Note To Self - Adding An SCCM Upgrade Package
This gave a lot of grief. There was some pointing fingers: Update your ADK (which admittedly, I haven't done) Check folder permissions Check SCCM machine account permissions But in the end, it was a very simple and dumb fix. I had followed some website's instructions to convert .esd to .wim file . *And* I put it in a new folder (I mean, I thought that was the only file needed). Turns out that I needed to copy the .wim file back into the location of the .esd file, which was under .\sources. After that, I was able to add the upgrade package. Sheesh.