What to check Think of the computer as a car. You don't need to know much about how it works to drive one, but someone who does know should check it out before you buy, and you'll need a test drive. If an auction company or other seller won't let you inspect and try out the computer, walk away. Start up Turn it on and off a few times to check the internal power supply - a common problem. Components Does it have everything the seller says it does? With PCs, check the information that flashes up during startup (use the pause key). Your friendly expert will know how to find out more. On a Mac, choose "About this Macintosh" under the Apple menu; and also select the hard disk icon, File, Get Info. Viruses Ask the seller if they have scanned for viruses. Run virus checking software on any computer you want to buy privately. Hard disk A common and expensive problem area: a new hard disk drive will cost $200 to $300. On a PC, type "scandisk" at the DOS prompt or in Windows click Start - Programmes - Accessories - System - Tools - Scandisk. On a Mac, run Disk First Aid (usually in the Utilities or Apple Extras folder). Check for excessive noise and long file access times. Spare parts Mice and keyboards are cheap and usually interchangeable, but if something inside the case goes, you might have trouble sourcing parts, especially if the computer is more than about five years old. Big international brands like Hewlett-Packard, Compaq and IBM may have "proprietary" parts, which means they are not compatible with other brands. Fan These are a common source of problems. Listen for erratic or excessive noise when the computer is operating. Upgradeability Does the computer have the right type of extra or existing ports to add new video cards, or peripheral devices like a printer and scanner? Can you upgrade the processor? Monitor Look for a bright, sharp picture not dominated by one colour such as pink or green. Turn it off for a few minutes and then back on to see whether the picture reappears reasonably quickly. Check the brightness and contrast controls are working to their full extent. Compare several monitors. Keyboard and mouse Do all the keys work? (Try typing every key.) Does the mouse pointer move smoothly around the screen? What's inside? If you can, ask the seller to open the case and check for a dusty dirty interior. Ask an expert The next step is to find someone with real expertise in computers and software who can make a decent assessment of any model you want to buy. If you don't have an experienced friend to help, hire a computer technician ($50 to $100) and get them to do all of the above, plus tell you: · How well the computer is built internally. · How compatible the components are with common software. · Whether the computer will be able to perform functions you want. · More reliable information about upgrading the computer and getting spare parts. What about software? When you buy secondhand software, make sure the purchase is legal. This means: · The seller must not keep any copies of the software. · You must receive the original software disks, manuals and licensing agreement. · If the software is an upgrade, you must receive the original version and all subsequent upgrades. Microsoft software should come with a green certificate of authenticity. Microsoft's anti-piracy number is 0800 PIRACY (0800 747 229). If someone offers to sell you a "backup", do not accept it. Piracy issues aside, secondhand software is often a good bet: it costs less and these days usually comes on durable CD-ROMs. Check the CDs aren't scratched though, and scan any software with a virus checker before running it. .