Scheduled to open this month, the store is the first of four planned by the high-end Italian merchandiser, at an undisclosed (but undoubtedly extravagant) cost. The gadgetry hits you the moment you walk in, and doesn't let up until long after you've left the store. For the fashion perplexed, ubiquitous computer displays help you pick a pair of pants to match that shirt you're buying. If you're a hard-core fashionista, the database finds clothing in your size that complements what's in your closet. And if you need spousal approval before buying (you know who you are), log on to Prada's Web site, where images of the clothes you tried on that day will be loaded into your personal account.