With computer prices ever more volatile, buying new hardware can seem like an expensive round of Russian roulette. How can you be sure you're getting a good deal? Check out PriceScan (http://www.pricescan.com), which tracks retail prices for computer hardware, software and supplies (inkjet cartridges, ZIP disks and the like). Input the name of the product you're considering, and, seconds later, the screen displays prices culled from online retailers, mail order catalogs and magazine ads. PriceScan is free, but it can pay big dividends. In a recent check of Macintosh PowerBook prices, the difference between the high and low prices for identical laptops was a staggering $1,249.