This screen shot is of version 6.1. If by deleting the Houdini directory you mean manually deleting all houdini files in C drive after uninstalling, I did that too.
Just last night by some miracle, I went under “Settings” then “Desktops” and tried deleting both “Build” desktops listed, but only one was deleted. The other “Build” desktop couldn't be deleted, but I ended up closing and reopenning Houdini afterwards and the error was gone.
Before I had done windows search and deleted “build.desktop” file to no availe, but going through Houdini's Desktop settings seemed to have gotten rid of the corrupted file!
I had actually meant the houdini6.1 directctory within Temp (see the path in the status bar in your screenshot). Glad that the problem worked itself out though anyhow.