Windows 7: Quick Indexing question.

I didn't realise the indexing service was still running on my computer, so I've just disabled it.
However, I know that you can disable it per-drive - although it seems to do something when you click apply (?).



So my questions are:
If you've disabled the service, is there any need to disable it per-drive (properties/general) ?
And secondly, what is happening when you disable it from a drive and it spends a few mins churning away ? (just curious)