Well indexing can be confusing. Some people say turn it off so it saves resources or whatever. But I also hear that it takes no resources. It just indexes and probably when then system is idle.
When an index is created, your searches will be faster. It's kind of like a library with no alphebetic index cards. Without the index, you have to search book by book. That's how the computer does it, with an index, it can find stuff faster, without it, it has to search from start to end.
I have my indexing service turned off because I just don't do searches often enough (I know how to organize my files
). But your situation may be different.
A lot of people use more powerfuly indexing programs than the built-in Windows one, like Google Desktop Search or Yahoos or Microsofts. If you have a 3rd party desktop search program, then disable Windows.
Think of any online search engine as a giant index. Google is an index. Imagine if you searched for something, and Google had to start from one end of the Internet and search to the other! Well out of 70,000,000,000 pages on the Internet, one search would take a year without an index!
As for your old hard drive, simply because it's older and been used a lot, a FULL format would probably benefit.
