Your command line is set properly, it defaults to the user path. What happened was that your environment variable for the PATH got changed (it was replced instead of appended to). That PATH variable is what Windows uses to find location of programs you type if you don't type in the full path to it. If you type in C:\Program Files\Microsoft Office\Winword.exe it will start Word. If you type in just Winword.exe it will also start Word, IF the PATH contained the line C:\Program Files\Microsoft Office\. Windows then knows to try to find the winword.exe command in that location.
Sometimes there are bugs in programs or someone did a bad job of repackaging a setup where the program should Append to the end of the PATH, but instead it Replaces the PATH with what it puts in.