I have an AMD Sempron 140 Sargas 2.7GHz (http://www.newegg.com/Product/Product.aspx?Item=N82E168...) that I put in a HTPC. It's been up and running a a few months now and I find the noise from the stock CPU fan to be an annoyance. It gives of a bit of a high-pithced whine that I can hear above anything but loud talking and action. I even have it stowed in a cabinet underneath the TV and I can still hear it.
Any suggestions on what I can do to mitigate the sound from this fan?
What type of case do you have? If you have a regular tower, you'll have quite a few options. You'll want something with a big fan. Big fans spin slower so their quieter. Here's a very nice one for $30 if it will fit in your case: