You can grab it here.

This program requires the Visual C++ 7.0 C runtime libraries.

Version history:

1.01: Supports the Brood War 1.05 installer.
1.00: Supports the Starcraft 1.00 installer.

The program can also switch an install from "Spawned" to "Retail" and vice versa. You need to have either your Starcraft or Brood War CD handy to run it. Place it in your Starcraft directory and start it up to use it.

Unfortunately, enabling spawn does not work with Brood War - it'll refuse to start if you turn it on, at least until you disable it again. However, even if it did work, Battle.net would ban you for trying to log on Brood War spawned, so not much is lost.

Credits: Skywing - Programming & Research, DarkWizzard: Research, ShadowFlare: SFMPQAPI.