I know how annoying it is. It sucks big time this tool developed by Microsoft which eats up all the memory on my computer. Even though its good to look for mails instantly on outlook, but it keeps increasing its memory usage.
You can disable it at startup only by the following registry keys:
Goto the above key and search for Start. In start Key type zero to disable searchindexer at startup only. But there is a catch to this, if you explicitly try to start the search indexer then this will enable the exe to start a service again. So you will have to use taskman to stop the service.
Tell me how it goes.