Which Windows Services Can You Safely Disable?

Peyote, unless you are a PowerUser on par as Calendar over in sevenforums, or as dalchina [and others] here, I would recommend not experimenting with Windows services or with msconfig -- until after you can make full images of your OS partition and your Data partition onto trusted external media with one eye/one hand tied behind your back. Experimenting with services, startups, etc. may cause much more grief than joy, thus can lead you to pull out your Windows install DVD or activating your factory restore partition or pulling out your OS backups.

Note that if you disable Windows indexing, I think you won't be able to search Settings, and that's useful. (I once made a change to indexed options that stopped that happening, so that's a reasonable assumption).

By default, the number of items indexed is pretty minimal, and once indexed (so quick you shouldn't notice it) it uses no resources so has no impact.