Sometimes the standard reinstall method may fail due to issues with the drive or Recovery partition, in which case you’d need to use Internet Recovery to reinstall Mac OS X instead as described here. 7 Lion did away with recovery disks, and these days, Apple provides a built-in recovery system within Yosemite. Start your Mac and hold Command +.
We've had a number of questions recently about searching in Mac OS X 10.5.6. As we explain in knowledge base article, Apple introduced a bug in Mac OS 10.5.6 that causes it not to correctly send search requests. Group Logic has been working with Apple and encouraging them to fix the problem in 10.5.7. We'll post an update as soon as we confirm that a fix is available. Until Apple releases a fix, there are a few workarounds.
One is to simply stay with 10.5.5 for now, if feasible. Another is to use a free tool called Find Any File, as described in knowledge base article.