Answer to your questions.
Type Services.msc in the start.
For the Search, scroll down to "Windows Search" Double click it and mark it as Disabled.
The facility is not one I use. The only real things I search for are my own files, which is done more quickly, manually.
Now scroll up to "Superfetch" and disable this.
This is a controversial feature. It was also in XP but the mechanics of its operation have been altered. You can read plenty on the web about its use but, briefly, what it does is stores your frequently used programs in a subfolder in the "Windows" folder. Every time you start, these shortcuts are loaded into your ram so that the programs can load more quickly. If you disable it, you will find your popular programs, even Firefox or IE, will (ONLY on the first access) load very slowly. After that the normal prefetch system will be in operation and the shortcuts will be in Virtual memory until you switch off. The downside is that it does use a little ram and, of course, does "thrash" (?) you hard disk whilst rearranging everything. ( Every access)
In your "start" menu you will find the Defrag program. If you click on it, you can disable it or rearrange the schedule. After SP1, you can also select which portion of your computer you wish to defrag.. By default, it runs every Wednesday. It has some intersting geometry, which you can also read up on. Microsoft decided (rightly, in my opinion) that it should be a back ground operation. You will find that, on the first defrag, it will take a re...ally long time. One reason is that it is shadow copying whilst defragging. After that, if you leave it on schedule, I doubt you will notice it's operation unless you are constantly installing new programs.