Maintenance

Antivirus (uses low memory usage).

Anti-spyware with an automatic cleaning engine (including heuristics to detect unknown threats)

Check if you're protected from viruses, spyware, network intrusions & other security threats.
Also try PC Security Test which simulates attacks & monitors the responses of your software.

Cleans temporary files, cookies, history, etc.

A simple & strong firewall that uses low resources (check out this leak test which shows Comodo Firewall to be the strongest) Open specific ports for Emule or BitTorrent
For an advanced Firewall, use Snort and read this tutorial

Hunts down & paralyzes threats that are too new or clever to be recognized by other software

Safe registry cleaner

Customize Windows user interface, optimize system settings, optimize hardware settings, customize Windows application settings & controll user environment with policies.

Fix many Windows problems using this detector & remover. Paste your log file here to get information of what you should delete. Also read this quick tutorial.

Super spyware & adware cleaner, installs the major spyware programs automatically, automates cleaning & chooses options automatically.

Protects your internet connection at any Wi-Fi hotspot or wired network.

Monitors for changes to any of the startup folders, registry keys & any files you want.

Run programs & browse the internet while disabling hard disk write access

Creates a virtual encrypted disk within a file & mounts it as a real disk. Encrypts an entire hard disk partition or a storage device such as USB flash drive. (many options & features)

Lock individual windows with a password.

Voice Biometric Logon and File Folder Protection

Disable some built-in update & authentication in WinXP (choose which you want to keep)

Optimize performance (PagingExecutive, LargeSystemCache, IOPageLockLimit) more info

Important WinXP SP2 Internet fix (100 half-open connections instead of 10)

Watch processes' memory usage, cpu usage & more. When processes reaches a certain limit, get a warning, close them, run a program, change priority, hide/show & more

Monitors cpu usage of processes & reduces the priority of the ones that overload your cpu.

Free up unused memory & eliminate memory leaks.

Internet optimization (read the FAQ section for more information).

Setup how many seconds after Windows has started, to load each program.

Securely encrypt & decrypt files.

Easily hide your private folders.

Fast defrag, low memory usage, screensaver version, can defrag USB sticks.
SpeeDefrag restarts your computer & loads the MS defrag.exe program before other programs
DefragNT has many options & advanced defragmentation)

Extract & create virtual cd/dvd image files (supports iso, uif, bin, cue, img, nrg, vcd, etc., create files up to 300mb.)

Creates virtual drives from virtual cd/dvd image files (supports iso, uif, bin, cue, img, nrg, vcd, etc.)

Hard disk partitioning and data management tool

Show how many MB each folder takes. If you want to see the space of each folder with visual blocks use SpaceMonger or SequoiaView.

Unlock locked files in WinXP

Compressing & decompressing utility (If you need to edit or create .CAB files use TUGZip)
To remove the trial notice in Winrar download this free WinRAR key.

Powerful dual-pane file manager with tabs & bookmarks

Backup manager

Periodically synchronize folders on Hard Disk, Floppy, LAN, USB Key, CD-DVD & FTP server.

Saves, visualizes & restores the MBR or any specified sector from any hard disk

CD & DVD data recovery (also try Roadkil's Unstoppable Copier)

Undelete & data recovery

Saves whole partitions

Stand-alone undelete (no install required)

Shows drives information, by type, volume label, vendor information & more.

Process manager (alternative to the standard Task Manager) (CTRL+ALT+DEL)

Windows Task Manager addon, get the latest definitions & advice on all the processes.

Printer manager: print preview, network support, multiple printers, export print jobs & more

Uninstall manager with an advanced algorithm that can uninstall programs that have a broken uninstall
Also contains: Auto Start Manager (manage which programs will start with Windows), File & History Cleaner, Unrecoverable Delete Tool & more

Shell extension manager (right mouse button menu)

Startup manager (choose which programs startup with your computer)
Use Autoruns if you want more startup items but a more complex interface)

Scans your computer for installed software & gives you a list of download links for the updates

Connection Keeper prevents your Internet connection from appearing idle or inactive.

Repairs various Windows problems, such as: Windows update errors, SSL, HTTPS, cryptography service (signing/verification) issues, COM/ActiveX object errors & more.

When you run this, explorer.exe & iexplore.exe are terminated, and a new explorer.exe is created.

Thorough, stand alone memory test for x86 architecture computers.

Password recovery (Dialups, Outlook, Mozilla, MSN, Yahoo Messenger, Trillian, etc.)

Notifies you about problems in your PC & helps you fix them.

Stability testing utility that can also stress test your PC.

A screen saver that fixes bad pixels on LCD screens (60% chance)

Fixes taskbar problems

Helps you find what those unknown devices in Device Manager really are.

Scans web servers to identify security problems & weaknesses

Enables two computers to share an internet connection through a serial cable (no network).

Share a single mouse & keyboard between multiple computers with a different OS

Manage your network enviroment (Automatically scan all devices within specified subnets, draw & layout a map of your networks, monitor services of your devices & more.)

Dial up enhancer (data, cost, POP3 mail checker, finger, ping, web notify tools & more)

Automatically identify your computer's BIOS & other system information.

Builds a detailed profile of your installed software, hardware, hotfixes, anti-virus & more

Gathers information on your CPU, motherboard, memory & operating system.

Shows hardware heat levels

An advanced system monitoring & desktop enhancement engine (contains system information, weather reports, news headlines & much more)

Change fan speeds, view hardware temperatures, check hard disks using S.M.A.R.T. & more.

Enables use of Java applets & programs.

Contains DivX, Xvid, Quicktime/Realtime Alternative, Media Player Classic, etc. If you have a media file that doesn't play, try to use Gspot which tries to recognize which codec is missing.

Some applications require Microsoft .NET Framework.

NTFS Bootdisk, Win 98, Dos, Linux, etc.

Reduces electricity when your computer is idle (reduces harmful CO2 & lowers your electric bills).

Retrieve your Product Key used to install Windows & save it to text or print it for safekeeping.

Quiet down grounding & motherboard noises. (select PictureSaver screensaver)

Enables you to remove the Microsoft "Windows Genuine Advantage Notifications" tool.

Fix WinXP annoyances & customize a few tweaks.

Create a GUI NTFS Boot CD containing many useful utilities & custom files of your choice.