Disk Utility, Installer, System Profiler and Software Update won't open.

[GnarlyMac101]

I am using a MacBook Pro OSX 10.4.11 (Tiger) and the Disk Utility, Installer, System Profiler and Software Update won't open. It all started when I was downloading as I normally do when ever I download a program from a trusted site I have previously used by CNET. Anyhow when the download completed with the .dmg file to begin to open, Safari crashes. I re-open Safari and I check the download window and the file for the program is in there. I click on the file and the double flash of the icon reacts but the file does not open. Installer shows up in the toolbar but it won't open the file. When I proceed to Applications>Utility folder>Installer and do a double click to try and open it, Installer won't open and then I tried opening Disk Utility and double clicked and nothing, it won't open, the same happens for System Profiler, nothing they all won't open. I go up to the apple icon in the left top side and scroll down the drop down menu to select software update and that won't open either. Prior to this happening I have noticed that when using Safari, it tends to load up web sites a bit slower and when I perform my 4 corner hot spots it tends to get stuck in the process for a quick 2 seconds or so. Anyhow, I can't get the Disk Utility, Installer, System Profiler and Software Update to open. Please help me I need this fix as my applecare has ended and doing my own google search has become frustrating. Thanks.