Full-forum searching has been enabled and disabled (and discussed) in the past, but Ian has it off because it's such a system resource hog.
If people were more intelligent about where they post in the first place, the searching would be more effective. Every time a post is in the wrong forum (like this one

and gets moved (like this one

it puts another glitch in the index resulting in a "you have requested a topic that does not exist" notice. If you search General for "overheat" in the last day, you'll get a hit on this thread, but if you click it, it'll do just that... See what I mean?
Brent