There are plenty of applications out there that can do wonders for your PC’s performance. Best of all, many of them are completely free to download and use. These programs help you remove unwanted system files, stay protected from malware and other harmful files, defragment your drives, and control what programs automatically startup at boot. Here are the best tools for speeding up your Windows XP or Vista computer.

Free disk defragmenter that is simple, clean, and easy to use. It doesn’t have all the advanced features that PerfectDisk has, but it's completely free to use and does an excellent job defragmenting your drives and speeding up your computer. You can visually see what the program is doing as its running and it tells you the number of files that have been scanned and defragged.

Extremely useful and effective PC cleaning tool that removes unused files from your system, increasing performance and freeing up valuable disk space. CCleaner also scans your registry for issues and then allows you to backup it up and fix the problems automatically. A program uninstaller is also included that removes all traces of uninstalled software. This tool is fast, easy to use, and will significantly speed up your system. Most importantly, it’s complete free to download and use.

Applications running in the background is one of the largest contributors to a PC’s slow performance. AutoRuns displays a comprehensive list of all startup monitors and programs scheduled to run at boot or startup. You can then choose the ones that you do not want to run, resulting in increased performance and faster boot times. Similar in functionality to MSConfig, but much more powerful.

Is your computer's performance bogged down by malware, trojans, and other junk? This anti-malware tool is fast and effective. This free app has a clean, simple interface and does an excellent job finding and removing malware without giving false positives. You can scan multiple drives or individual files and FileAssassin is included for removing locked files. Real-time protection and scheduled updates and scans require the paid version, but the free version will suffice for most users.

PerfectDisk is a top notch disk defragmenter with several advanced features and a slick, easy-to-use interface. Standard defragmentation is fast and effective, and offline defragmentation lets you defrag system files that can’t be modified while Windows is running. You can also use the AutoPilot feature to automatically schedule disk defrag passes daily or weekly. While Auslogics is a better choice for most home users because it’s free, PerfectDisk is a better choice for advanced users and IT staff.