Setting the FBS to 266 on an AMD chipset is extremely high.
On a CPU that has been running at stock for that long it may not be a good idea to clock it. But if you must, try raising the FBS to 212 and go up 2 steps at a time (ie... 212,214, 216....) testing for stability and keeping a close eye on temps. You can raise it until you get a bluescreen or excess temps. When you get to that point go back 2 notches and you should be good to go. And do not raise any voltages, as that will surely be the demise of your CPU!
Fester