Warning: This list is for advanced users.
Use these apps ONLY if you know what you are doing or use them at your own risk.

nCleaner - advanced system and application cleaner
Every computer needs care, and care starts with maintenance and cleanup.
Good stuff on nCleaner: Junk finder, Reg Cleaner, Free Space Shredder, Tweak manager, Startup manager and few more.

Note: because nCleaner is an advanced system app, you shouldn’t use it unless you know what you are doing. As an alternative, use cCleaner.

DriverMax – detects, downloads and installs the latest version of your computer’s drivers.
It also backs up all drivers and lets you restore them.

SmartDefrag – Defragmentation is a very important process in keeping your hard drive’s performance at maximum and bring its files together.
SmartDefrag will diagnose and optimize your machine’s hard drive while running quietly in the background.
As a prevention, this defrag app will pause itself down if the CPU raises over 40% .

Lingoes - the little sister of Babylon is a dictionary and translation freeware.
So what’s so special about this app that makes it a “must have” tool?
With Lingoes you can:

lookup dictionaries, do full text translation, cursor translation, zoned word translation and pronunciation of words in over 80 languages.

It also contains some of the most popular and reliable thesaurus dictionaries such as: Cambridge, Longman, Collins, MacMillian…and few more.

Revo Uninstaller – this tool does more than its name says and it does it good.
The uninstaller is just an amazing tool. With few clicks it will not only uninstall your apps, but it will also do a deep registry key scan and find the dead file paths or leftovers giving you the opportunity to actually do clean removals.
The other tools included: junk file cleaner, autorun manager, windows tools, evidence remover, unrecoverable undelete….and few more.

These are the 5 essentials, all compatible with Vista and XP,  and you should get them.