Back in the bad old days of computing, hard-drive defragmentation was a big deal. You needed a quality third-party “defragger,” and you needed to run it regularly—at least once a month—to ensure optimal system performance.

Times have changed. Although computer files still get split into fragments and scattered across your hard drive’s platters, the computers and drives themselves are so much faster now that fragmentation isn’t the same performance-wrecking problem it once was.

What’s more, if you’re a Windows 7 user, you really shouldn’t have to worry about fragmentation at all. Check out these three important facts about hard drive defragging:

1. In Windows 7, the built-in Disk Defragmenter utility runs automatically at scheduled times, usually once per week. This happens by default, so chances are good your hard drive is already defragged. And by most accounts, the utility compares favorably with third-party alternatives, so don’t spend money on another defragger unless you have very specific reasons for doing so.

2. You don’t necessarily have to leave your computer on overnight. If Disk Defragmenter isn’t able to run at, say, 1 a.m. Wednesday, it will kick in the next time your computer is idle.

3. You should never defragment a solid-state drive (SSD). Doing so can shorten its lifespan. In fact, whether you purchased a laptop with an SSD installed or upgraded your laptop with one, be sure to disable scheduled defragmentation in Windows 7. Click Start, type disk, and then click Disk Defragmenter. Click Configure schedule to disable the feature.

By the way, if you have an external hard drive, one that’s not always connected to your PC, it may not get the chance to benefit from Windows’ scheduled defragging. Therefore, you should run Disk Defragmenter on it manually every month or so.

For more on the subject, read Lincoln Spector’s Defragging: How, Why and Whether.

Contributing Editor Rick Broida writes about business and consumer technology. Ask for help with your PC hassles at hasslefree@pcworld.com, or try the treasure trove of helpful folks in the PC World Community Forums. Sign up to have the Hassle-Free PC newsletter e-mailed to you each week.