Ok... lets simplify... Forget "Temp" and "%temp% ... no matter what you are naming it, you are creating a shared folder where "Everyone" has full access. You can call it Common, Shared, MuppingSnarf, whatever you like... you're creating a shared folder.
This is actually relatively trivial on Windows... Create a folder --any folder, anywhere on your system-- right click, properties, sharing, share the folder and set "Everyone" to have full control. It's done. Anyone who sees that can use it...
There's no need to make it any more complex than that.