From: http://www.wikihow.com/Dramatically-Speed-up-Windows-XP

Improve swapfile performance 2. If you have 4Gb of RAM, you will discover that Windows XP
is unable to use it all. Typically XP is limited to about 3.25Gb - so you have approx 
.75 Gb of hidden RAM that is can be used for a high speed swap file. To get access to 
this free RAM, use the totally free 'VSuite Ramdisk Free Edition' RAM Disk utility.

From: http://www.blackviper.com/custom-services-registry-file-creation-tool/windows-xp-custom-services-registry-file-tool/windows-xp-home-service-pack-3-custom-services-registry-file-tool/

  Configuration Information

  Automatic ~ With a service in this state, it will start at boot time. Some services, 
  when no longer required, will also automatically stop when not needed. However, this 
  is very rare. If you find you do not need a service, place it into Manual or Disabled.
  
  
  Black Viper’s Windows 8.1 Service Configurations
  Service names

http://www.donationcoder.com/Software/Mouser/proctamer/index.html

Process Tamer is a tiny (140k) and super efficient utility for Microsoft Windows XP/2K/NT/Vista/Win7 that runs in your system tray and constantly monitors the cpu usage of other processes. When it sees a process that is overloading your cpu, it reduces the priority of that process temporarily, until its cpu usage returns to a reasonable level.

From: http://www.steffengerlach.de/freeware/index.html

  Scanner - This tool uses a sunburst chart to display the usage of your hard disk 
  or other media. The chart shows all major files and folders from all directory levels at once. 

http://www.uderzo.it/main_products/space_sniffer/download.html

SpaceSniffer is a freeWare (donations are welcome) and portable tool application that lets you understand 
how folders and files are structured on your disks. By using a Treemap visualization layout, you have 
immediate perception of where big folders and files are placed on your devices. Treemap concept was 
invented by Prof. Ben Shneiderman, who kindly permitted the use of his concept into this tool. 

From: http://www.splashsoft.de/Freeware/ridnacs-disk-space-usage-analyzer.html

  RidNacs RidNacs is a very fast disk space usage analyzer for Microsoft Windows. 
  It scans your local drives, network drives or single directories and produces a tree 
  view with a percentage bar chart column. This gives the user a quick and easy way to 
  identify the largest directories and it's very useful for cleaning up the disk.
  

From: http://www.techsupportalert.com/best-free-disk-space-analyzer.htm#JDiskReport

  Best Free Disk Space Analyzer

http://www.derlien.com/

Disk Inventory X is a disk usage utility for Mac OS X 10.3 (and later). It shows the sizes of files and folders in a special graphical way called “treemaps”.

If you've ever wondered where all your disk space has gone

http://grandperspectiv.sourceforge.net/

GrandPerspective is a small utility application for Mac OS X that graphically shows the disk usage within a file system. It can help you to manage your disk, as you can easily spot which files and folders take up the most space. It uses a so called tree map for visualisation. Each file is shown as a rectangle with an area proportional to the file's size. Files in the same folder appear together, but their placement is otherwise arbitrary.

http://www.javacoolsoftware.com/spywareblaster.html

Spyware, adware, browser hijackers, and dialers are some of the most annoying and pervasive threats on the Internet today. By simply browsing a web page, you could find your computer to be the brand-new host of one of these unwanted fiends!

http://www.safer-networking.org/index2.html

free, fully functioning privacy and anti-malware software brought to you for over 10 years by Safer-Networking!

http://www.mydefrag.com/

MyDefrag is a disk defragmenter and optimizer (a maintenance utility to make your harddisk faster) for Windows 2000, 2003, XP, Vista, 2008, Win7, and for X64. It is freeware, no time limit, fully functional, no advertisements. Fast, low overhead, with many optimization strategies, can handle floppies, USB disks, memory sticks, and anything else that looks like a disk to Windows. Included are a set of easy to use scripts for endusers, a scripting engine for demanding users, a screensaver, and a combined Windows plus commandline version that can be scheduled by the Windows task scheduler or for use from administrator scripts

http://hddscan.com/

  HDDScan is a freeware utility for hard drive diagnostics (RAID arrays, Flash USB and SSD drives are also supported).
  The program can test storage device for errors (Bad-blocks and bad sectors), show S.M.A.R.T. attributes and 
  change some HDD parameters such as AAM, APM, etc.

http://lifehacker.com/399102/hddscan-performs-hard-drive-diagnostics

http://www.hdtune.com/

35.00

HD Tune is a hard disk utility with many functions. It can be used to measure the drive's performance, scan for errors, check the health status (S.M.A.R.T.), securely erase all data and much more.