Application to change fan speeds on the fly?

[Morthoseth]

My computer makes a lot of noise as it stands, and turning the fans down make a huge difference - is there any application i can use to change between two profiles, gaming and non gaming? I'd like ideally to lower all fans to 30/40%.

 

[SillyHeatsink]

I think you can use SpeedFan, not 100% sure since I don't use it personally.
I use physical fan controllers (basically variable resistors in series with the fan), I find them much easier to deal with. If your case allows it, this would be my preferred option - Zalman make a decent fan controller that can control a few fans at once, worth a look.