I highly doubt you would get any sort of overclock on those graphics
'Integrated Intel GMA 4500MHD graphics' Absolutey NO point, I doubt you would get any sort of overclock or even decently stable to make it worth it while.
And as for CPU, well, since you have a Dell (Meaning a very locked down BIOS), i doubt, again, you would be able to overclock, i should'nt think you could hit 2.5Ghz, let alone 3.0Ghz.
And don't even think about using software inside Windows to overclock the CPU, it will just cause issues and probably instability.
Take it from us mate, i am not being horrible but please, save yourself the heartache. If you like gaming that much and want some decent performance, get a desktop or a gaming laptop.