Just one note to this. Index is used by programs that use the libraries. In your case just removing the download folder from the indexing may have been enough.Ran into a problem of my SP3 fans going insane whenever I'm downloading stuff. Looking at Task Manager, something called Microsoft Search Filter Host was constantly taking up 30% or more of my CPU.
After a bit of reading it seems like this is Microsoft's feature that indexes pretty much all the files on your system. Since I don't really use this (I keep my files pretty organized) and just use the search feature for control panel stuff and programs, I decided to disable it.
SP3 has been quiet as a mouse ever since with CPU usage constantly under 10% (usually around 5-8% or so).
This isn't for everyone but if you don't use the search feature for looking up your files or don't mind a *bit* of lag when searching for different functions, you might find it beneficial.