Buying a computer, even a used one, is a big decision that requires keeping a few things in mind. Fiordaliso/Getty Images If you’re looking to buy a used or refurbished PC, there are some important things to look out for. Avoid buying a computer that’s more than three years old, and watch out for components that are out of date or obsolete. If you’re getting a used laptop, make sure the battery holds a charge and works properly. Visit Insider’s Tech Reference library for more stories . A new computer can be expensive, and like a car, it loses a lot of its value the moment you take it home. There’s a huge marketplace of used computers out there, which means you can potentially save money, but you should be aware of some common pitfalls before you buy your next used PC . 5 things you should know before you buy a used PC It pays to understand a few rules of the road before you bring a used PC into your home or office. Avoid computers that are more than about 3 years old Moore’s Law is a rule of thumb in the computer industry that predicts computers double in performance about every two years. That’s still roughly true, but the overall pace of personal computer innovation has slowed in the last decade. A computer from 2017 looks and performs roughly the same as a computer from 2020. But as you head further back in time, PCs start to show their age — the CPU will be noticeably more sluggish, the computer will lack USB-C connections for modern mobile devices, and the stock hard drive size will shrink to claustrophobic levels. The bottom line is that computers more than about three years old will likely need to be replaced sooner — making them a bad investment. Keep an eye on the specs If you’re getting a computer that’s a few years old, it may be hard to know if you’re getting a good value, especially if you don’t stay current on computer tech. First and foremost, avoid computers with hard disk drives ( HDDs ). Consider a solid state drive ( SSD ) absolutely mandatory, regardless of the computer’s age. It should also be at least 128 GB in size; some older PC laptops came with tiny 64 GB SSDs that are almost unusably small. As for the processor, look for a 7 th generation or later Intel Core CPU . You can tell because it’ll have a number like -7000, -8000 or higher, like Intel Core i5-8400. Anything older than 7th generation, or a budget CPU like a Celeron, will feel too slow. You should also look for full HD IPS displays . TN-based screens will look dull and washed out, and resolutions less than 1920×1080 won’t give you much screen space to work with. Check the laptop’s battery The single most critical component in a laptop is the battery, and an aging (and failing) battery is the most common reason why someone would sell their old laptop. If you buy a used machine, test the battery right away: Make sure you can charge it to full, and then run the laptop until the battery dies. If you have time, repeat the test a second time. If you find that the battery can’t hold a reasonable charge, you should probably return it for a refund, unless you can replace the battery inexpensively. Keep in mind that it might be hard to get a replacement battery for an older laptop. Wipe the hard drive before you start to use the PC Can you trust a used computer’s hard drive? Probably not — it might have malware installed, even if it appears to be wiped and ready for use. That’s why it’s a good idea to wipe the hard drive yourself before you start using a used or even refurbished computer. Stick with refurbished computers You can find computers billed as both “used” and “refurbished.” A refurbished laptop or desktop PC has been inspected to make sure it’s working, comes with a warranty, and often has worn components replaced to return it to like-new condition. This is especially important for a laptop, which should have a new battery installed. Various manufacturers sell factory-refurbished computers from their own website — check out Apple , Dell , HP and Best Buy’s Lenovo page , for example. A used computer is just that — used. It’s usually sold as-is and isn’t backed with a warranty. While you’re generally safer buying a refurb, a used PC might be okay as long as you can return it for a refund if anything is amiss — be sure to test it quickly and thoroughly after you buy it. Related coverage from Tech Reference : How to wipe a hard drive and data drives on a PC or Mac computer and reduce the chance of someone accessing your files What is an external hard drive? One of the best ways to protect your important files, explained SSD vs. HDD: How to decide which storage option is the best for your computer Why is my PC so slow? 7 ways to speed up a lagging computer Why won’t my PC turn on? 10 ways to troubleshoot your Windows computer when it fails to start Two crossed lines that form an ‘X’. It indicates a way to close an interaction, or dismiss a notification.