There are many large shopping centers in Hanoi. You might start with Trang Tien plaza (Trang Tien st. and Hang Bai) or Vincom Towers (Ba Trieu street near Le Dai Hanh)

There's also Big C shopping center (in the SW of the city out in Cau Giay) and another place that I pass near Lenin Park that advertises Gucci, etc.

And a new Vincom like shopping tower will open up on June 30, 2007 according to their newspaper ad - Ruby Plaza on 44 Le Ngoc Han. They advertise as selling name brand stuff one would buy on Valentine's - jewelry, perfume, leather bags, etc.. Funny still under construction website here: rubyplaza.com.vn

Vincom on Ba Trieu and the new Pacific Place on the corner of Ly Thuong Kiet and Yet Kieu are both good bets.

Ultimately you can find a weekend, fly down to Bangkok or Kuala Lumpur. There you don't even have to post a question in the webpage to ASK !!