Well I have a new windows 8 computer (1 month old) and when I play monster with my video settings on low I only get around 24-36 fps, I increased the ram in the settings to 7.25, what else can I do?
And looking up the specs on Pavilion 23's, I'm going to say your biggest bottleneck really is your CPU, an AMD E2-3800 APU, which isn't that powerful of a CPU when you get down to it, especially since it's acting as both your CPU and your GPU.
Yeah, that processor is basically a giant steaming turd in terms of performance. A dedicated video card might help a bit, but Feed the Beast is very processor intensive. Try lowering your memory usage to 4 gigs and taking out some mods that you won't be using or play a less intensive pack like FTB Lite.