Hundreds of years ago, maybe thousands, computer stores were staffed by smart people. You had to write your questions down before you went in the store so you wouldn't get snapped at. Now the big-box computer stores are staffed by people who got fired by Wal-Mart for not being smart enough. You hope they won't ask if they can help. Ah, but there is an oasis of know-how: Micro Center in Richardson, in the Keystone Plaza on the southbound service drive of Central Expressway, half a mile south of Spring Valley Road. They build their own line of computers, stock all the peripherals. Great deals. Lots of really capable salespeople. Can't last.