LaTeXDaemon is a tool that allows you to precompile the preamble of a latex document in order to speed-up the compilation process. It runs a daemon in the background (using almost no cpu resource) that recompiles the document every time it is notified by Windows that the .tex file, the preamble file or some of them dependencies have been modified. It also compare the MD5 digest of the files that are being watched so that recompilation is triggered only when really needed.