Remove Duplicate Files
Lurking on your hard disk are plenty of duplicate files that take up space for no reason. If they're media files such as music or photographs, they could be consuming hundreds of megabytes of storage. Finding them all can be tough because identical files may have different names, and even files with the same name may be sitting in different directories.
The US$20 DupeRazor Duplicate Files Removal Kit searches out duplicate files, tells you when it finds them, and then lets you delete them. It works lightning fast, zipping through several thousand files in minutes.
Be aware that it does make mistakes sometimes, so be sure to use its built-in ability to launch files to examine them before deleting them. If you'd rather not vet the possible duplicates so closely, you might prefer the more accurate (and, at US$30, more expensive) Easy Duplicate Finder.
Defragment Your Hard Drive (but Not Your SSD)
Here's one more reason your PC might be sluggish: The hard disk may be fragmented. Windows stores files in pieces, and as you open and save them, those pieces go to various parts of the hard disk, leading to fragmentation. When you open the files, your PC needs to work harder to find them across the many different pieces. Fragmentation is a bigger problem for older PCs, but even new systems reap a benefit from defragging: If you happen to lose any files, defragged data will be easier to recover. (Solid-state drives, however, don't need frequent defragging; for more information, see "Defragging: Why, How, and Whether.")
You can solve the problem with the free Auslogics Disk Defrag, which finds fragmented files and then stores all the pieces in each file contiguously so that they open faster. You get a lot of control over how to defragment your hard drive, including setting a defragmentation schedule and determining what priority Auslogics Disk Defrag should get if it works while other programs are running. You can even move system files to the beginning of the hard disk, which may help performance.
Make Your PC Boot Faster
PCs seem to take an eternity to boot. That's because many programs set themselves to run automatically at startup even if they're not needed, which makes your PC chug along at boot time while you twiddle your thumbs. And once your PC boots, it runs more slowly since too many unnecessary programs are loaded.
The free Soluto does an excellent job of correcting matters. Soluto runs in the background and examines what applications and services load during startup. Then it analyzes them, and -- using data from other Soluto users -- it groups them into programs that need to run at boot, programs that don't have to run at boot, and programs that might be required at boot. You then make the decision about which ones should load.
The result? A faster-booting PC -- and possibly a speedier PC overall.