GPU Fan going 100% all the time?

[Zapmaster]

So I have LL installed on a system with a Radeon 4870, it's a big old card with a loud blower fan, and it appears to constantly be running at 100% (or close to it). So it's very loud. Is there a way to limit the fan speed on it manually? Or are there drivers I should be installing so that fan ramps up with load? And I don't think it's the card overheating because when I log in to Windows Vista on the same system it's fan is quiet. Any tips would be great, thanks.