Well that sux and no, you shouldn't remove the purple thing
Looking at this: hhttp://www.build-your-own-computer.net/motherboard-diagram.html
That is the heatsink to the northbridge so yea, u must keep it there. The thing is that the 8800GTS is approximately twice as large as the normal video card with a heatsink, so I wouldn't blame you for your purchasing decision, but I wouldnt checked the mobo out b4 u bought the card to see if it would fit or not.
2 things u can do here, change the mobo or get a new video card. a radeon 4850 takes up 1 slot and is just as powerful as a 8800gts. That is my suggestion
Above I'm a proud Gran Turismo fan, not a Sony fanboy, and now a proud 360 owner, but sharing xbox live accts ATM
End of 2009 Predictions (made Jan 1, 2009): My predictions were pretty accurate, the 360 was over and the Wii was just under.
Wii: 65 mil (yea I'm crazy) 360: 35 mil (its getting there) PS3: 30 mil (the slim better do well)
End of 2010 Predictions (made Jan 7, 2010):
Wii: 81 mil 360: 47 mil PS3: 45 mil