Sluggish computers can be a real drag on productivity. What's more frustrating than watching a computer struggle to complete what used to be an easy task when then machine was new?

Most computers run slowly not because the hardware has become degraded but because of issues with memory. As users install programs and browse the internet, those files leave traces of themselves behind that aren't completely cleaned up even after deleting cookies and running program uninstallers.

Luckily, there are a host of apps that can easily and quickly boost your PC or Mac's performance by getting rid of unused files and freeing up disk space. Here's a look at five that you might find useful:

1. Revo Uninstaller
After Windows users run the Revo Uninstaller, this app goes back and clears related files and programs that Windows might have missed in its own cleanup process. The app lets users customize their level of uninstallation, from light to deep, and a "hunting" mode that can pinpoint specific tasks and files to eliminate.

The trial version is free, but users who want to unlock some of Revo's more powerful features will need to shell out roughly $40 for the pro version.

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2. AppZapper
Mac users running OS X can uninstall programs via the AppZapper. Billed as "the uninstaller Apple forgot," AppZapper makes it easy to uninstall programs and their related files by simply dragging the program's icon into the app. One laser blast later and your hard drive should be freer.

It's a much cleaner and thorough way to uninstall programs than simply dragging them into the recycling bin. The trial version lets users have 12 "zaps" for free. After that, $12.95 will unlock the app's unlimited uninstallation power for life.

3. Flash Cookie Cleaner
Windows users can clean temporary files out of their internet browser's cache with the Flash Cookie Cleaner. Not only does clearing out the cache save you space, it also stops websites from tracking your browsing habits and can erase any saved logins in case you have to temporarily share your computer or are concerned about unauthorized logins for some other reason. Best of all, it's free.

4. Washing Machine
Mac users who want to quickly and easily erase their browsing and download histories, cookies and temporary files cache can find Washing Machine to be handy. The program is compatible with most web browsers and even some less obvious programs that also store personal data.

Users can schedule the app to scrub their data at a certain time of day and provides a smart interface that makes it easy to delete specific types of data with surgical precision. The app usually retails for around $10 but is on sale in the App Store for $7.99.

5. MemoryFreer
Need more space but there's simply nothing left to delete? Try MemoryFreer on your Mac. It's a tiny app with one job: to free up unused RAM at the touch of a button. The app is available for just $0.99.

Windows users can get a similar effect with Extra RAM, a free memory management program that adjusts your PC's memory usage as it runs in the background.

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