Cleaning & Speeding

Can anyone tell me what software i need to do the following:

1. Clean all the old files and folders left from old software that i have uninstalled.

2.Clean all the old files, dlls, temps etc not needed.

3. Using the best software thet will defrag hard drive (not using the Windows XP version).

4. Speeding up Windows XP, by freeing up the ram or other programs that slow down Windows XP.

5.A Software that will let me use a marine fish tank for my screen saver (Not Windows XP Bonus).
Or if using Windows XP Bonus ,to add more fish)