There are many boutique hotels in Hanoi Old Quarters. Luong Ngoc Quyen Street and surrounding streets are good starting point.

http://www.hotels84.com/hotels/ngocminhhotel/

http://www.hotels-in-vietnam.com/hot...e_1_hotel.html

http://www.hotels-in-vietnam.com/hotels_hanoi.html

http://www.clicktovietnam.com/hotels_hanoi_hotel.asp

No need to book in advance, just walk around the Old Quarters and you'll find plenty of choices. All prices are negotiable, so don't take their first offer.