Mark wants to know if all-in-one computers are a good deal. Leo says that Apple changed the game with the iMac and now other PC makers offer them to. They're elegant looking, but some are difficult to expand and upgrade. All-in-ones have thermal constraints as well, and some all-in-ones have a throttled processor because of the heat issue. But if he gets one, he should spring for the SSD and at least 8GB of RAM. It'll help his performance dramatically. That's really where performance is needed anyway. Then he should keep his data on a spinning external drive.
Should he get an antivirus? Leo says no. Most antivirus are notoriously inaccurate, open the system up to other threats, and do nothing for so-called "zero day exploits." Leo says for Windows, Microsoft's own Windows Defender is free and comes with the system. It's good enough. But the last line of defense is his own online behavior.