well, from what i hear, the best thing to do is to take a hair dryer to it, to heat the pink gooey glue that they used (like bubble gum) and then take a credit card, and lay it inbetween the chip and the heatsink, and take a flat head screw and pry the sucker off - - or twist the heatsink around until the glue starts to seperate - - those are what i've heard [u can also stick it in the freezer instead of using a hair dryer, and hope that the glue brittles due to the cold, so u can pop it off with a screw driver - i did that with a radeon ^_^, i didnt needa remove my NB heatsink yet, it is making fine contact, and my 125cfm cpu fan blows on it]
good luck, stay calm, and if u decide to use a screw driver, be careful, as i said, use a credit card to protect the mobo and the chip leads if the screw driver slips (trust me, it isnt cool when it does, i had a driver slip off my SLK-800 and it tore through my red glossy paint on the mobo tray leaving a nice size {and ugly} scratch on the mobo tray, luckily it missed the mobo!)
PS: If you feel like it, and have an extra little ram heatsink (like ThermalTake's blue ram heatsinks) or the old Northbridge heatsink, slap it on the southbridge with some Arctic Silver Adhesive - - some people (myself included) found that it helps for stability and helps keep down the static if ur using onboard sound. (just be sure to make sure there is clearance aound the heatsink, like, make sure it wont hit any little electronic thingies on the mobo - - and only do this is ur okay with possible voided warranties, being that iif the mobo goes bad, and u needa remove that southbridge heatsink, it may be difficult if not impossible, given the holding prowess of the adhesive!