One of the best Mac OS X utility around? TinkerTool
The features list is really impressive, so just download it and start tweaking your Mac OS X (10.1 to 10.4).
The tool makes sure that preference changes can only affect the current user. You don’t need administrative privileges to use the tool. With this design, it is no problem to use TinkerTool in professional networks where users have restricted permissions. The program will never change any component of the operating system, so the integrity of your system is not put at risk, and there will be no negative effect on system updates.