Indexing Service
NOT RECOMMENDED: Indexing Service create a lot of CPU and Drive activity - and it is continuous.
Indexing Service continuously monitors and indexes files, folders, their contents, and their locations. It will speed up searches for files/folders and also when searching for instances of a particular text string within files. Of course, if your system is not powerful it will slow you down.
If you perform a lot of searches it may be worth it. Try it, and if there is no apparent slowdown, keep it turned on.
To enable Indexing:
Start/Search . . . click Advanced Mode\Other Search Options\Change Preferences and click "With Indexing Service"
To Disable repeat the steps above but select "Without Indexing Service"