Thanks for all the replies.
Crankyman is right, it's not much of a heatsink (nor was it much of a fan. It's a little piece of crap.
I ran the card for a while and then figured out a way to attach my 'new' fan to it. Since the ATI fan has the heatsink 'molded' around it, I ended up attaching the 'new' fan to the OLD fan using bread-bag twist ties
The OLD fan is, in turn, simply attached to the heatsink as it usually would be.
So now the new fan is piggybacking the old one.
I'm not much of a gamer and when I do spend an occasional 15 minutes playing games on this PC, they're 80's arcade MAME games, so I really don't think it'll be a problem, but I'll keep my eye out for any video anomolies.