Have you ever visited http://www.nirsoft.net/ ?
There are many powerful tools in it. I will list down several of my favourite utilities from NirSoft:
RegScanner – Search the registry key, provide very good interface. You can this instead of the “Regedit.exe” built-in search.
VideoCacheView – This one is really powerful, which is recently added. If you are watching online video, the .flv file, then after finish watching, the video is downloaded in your cache. And using this utility, you can save the cached video to your folder. I haven’t try it with youtube, but I tried it in other websites using IE, and it works.
CurrProcess – I use this in order to replace Windows task manager before. But, finally, I stick back to task manager. However, this utility really provides a lot of information of the current process. Really nice.
ServiWin – This utility will display the installed drivers and services, and you can disable them using this utility.
There are a lot of utilities. But I only use a few of them. You can explore it, and find your favourtie utility. You might also like the password utilities.