The fan of my V7800 ATI FirePro videocard has recently gotten insanely noisy, and I suspect it's the dust in the fan. I took it out and tried to open it by loosening all screws, which took off the metal backplate, but the big shim or lid covering the other side and the fan are still there and I see no way to get it loose.
I found several posts on replacing the fan or even about cleaning up and one mentioned using a knife, but none was explicit. Though on this post on overclock.net the picture clearly shows it is possible and the user there managed to get the heat down after cleaning.
Any ideas on how to get the fan from from the shim/cover of the card?