Following on from our laptop buying guide of a couple of weeks ago, this week I’d like to bring to light a worrying trend. We have seen an increase in the number of second-hand computers being brought in which not only have faults but also have non-genuine operating systems installed. Often these are very old laptops but which have a more recent version of Windows (usually Windows 7 Ultimate) illegally installed on them. This isn’t about protecting Microsoft’s millions but simply that these older laptops weren’t built to run Windows 7 or 8 since manufacturers often don’t make the software drivers available for newer versions of Windows. The laptops we’ve seen recently were all very underpowered XP machines with a mere 1 Gigabyte of RAM and were purchased through places such as Facebook selling pages, Gumtree, boot fayres and disreputable computer shops. You might think that buying a laptop for under £100 is a good idea in these austere times, but do check what you are buying and make sure that it comes with the right version of Windows installed So how do you know that you’ve got the correct version of Windows installed? Firstly, you need to check that the laptop has a Microsoft Certificate of Authenticity (COA). This is a label, usually located on the body of the computer (or for some newer laptops, inside the battery compartment), which is used to identify genuine Microsoft software. The version of Windows printed on the COA should match the version of Windows installed. If the COA doesn’t match or is missing, the chances are that the operating system is not genuine. Most Windows 8 computers will have a Windows 8 anti-tamper label on the body of the computer, however the code for installing Windows 8 is often locked away inside the main board of the laptop so it can’t be stolen. For more assistance, try Microsoft’s website: http://www.microsoft.com/en-us/howtotell The general rule to remember is that if the price looks too good to be true, it probably is. People who sell dodgy laptops often advertise them at just below the normal prices to make you think you're simply getting a good deal. We always advise that you check before you buy and ensure you are buying from a reputable company. If you believe you have been a victim of this practice, talk to Trading Standards and Microsoft.