You don't give much to go on here. Are you running Cron scripts regularly? OS X requires these for optimal performance. Download MacJanitor (freeware) from www.versiontracker.com and run the scripts.
Cron scripts are part of the Unix base of OS X. They are maintence scripts that clear up files etc. The problem is that Unix was designed to work with the computer always on the the Cron scripts tend to run at night so that they often don't run on many users' machines. There are daily, weekly and monthly scripts.
MacJanitor is one of those 'must-have' bits of free software.
Yes, that's the line which will do all the periodic cron scripts.
And, index that hard drive if it hasn't already happened, then you'll probably be content with search speed. If it does not work you have the right to complain!