AMD 64 X2 pure power but sits unused due to loud fan and hot air

First and easiest thing to do - do you have AMD Cool'n'Quiet installed and operational?
Check with CPU-Z if your CPU downclocks when not underload.
If it doesn't, go to the AMD site, go to processor updates & utilities and download the driver suitable for your CPU and OS. Install the file and enable in BIOS. That'll make things cooler (and hence quieter!).
Check the CPU heatsink for dust and make sure any case fans are dust-free as well

are you sure its not HDD noise, this is often common with 5400rpm and early 7200rmp system, also system which dont have enough ram so are always caching things. the sound of a HDD is more like a giogometer (you know like to test radiation (No? oh well))
if it your HDD then you can replace it, or get a cage to fit interally inside a 5.1/4" drive bay.

however if it more of a low humm or whirring then it probaly the fans.

if its a hot room, then you really need a after market cooler, whihc are cheap as. take a look at the coolermaster hyper TX2 as recommended by the THG HS/F reviews. it also dirt cheap, and near silent.

you can replace your exghuast fan with relative ease and for a low price. again most aftermarket case fans form big name brands are quite, like scyth, akasa and coolermaster.

also if you dont have Cn'Q running as LBird said you should give that a blast.

if you fan are connected to your motherbaord look in your bios to see if active fan rate changing is enable are manually set, sometimes if plugged into the motherboard the MB throttrles them at 100% like as though they where plugged in to PSU via a Molex - 3 pin adaptor.

all in all i should cost you more than £20 ($40) to replace all the fan inside your case including your CPU fan.

while your at check to see if you have a northbridge chipset fan, this horrible 40mm fan are whiney as hell. you can have these replace by another fa. (scyth make a good 40mm fan) or by a passive heatsink.

if your motherboard has no way of controlling the fan and trhrottles then at 100% then invest in adrive bay fan controller.

hope some of this helps, i know i have had similar problem in past, & it allways been one of these.