Originally Posted by Davemeister
We had a borked installer once that was supposed to copy your path to a variable, append a new path, and then set your path to the content of that new variable.
What actually happened was that the copy your path to a variable part returned nothing and then your path only included the path to the new program. Ooops.
One time a client's custom inhouse designed HR system was updating environment values in the autoexec.bat and back in the 3.1 days. What it actually ended up doing was overwriting it with ONLY had the changes they wanted to make. I got to walk around for a few hours restoring the backup copies they fortunately made.