1) New Video Card -> $270 -> 68XX or 69XXseries would be great, and relatively cheap
2) New HDD ($115 + $65), better, A NEW shiny new 96GB/ 128GB SSD + 2TB HDD for storage will do wonders for you.
3) New faster 8GB of ram, 4x2GB Matched Kit - $120
$270 + $180 + $120 =[B][I][U] $570.
[/U][/I][/B][COLOR=Black]And I spent all of 5 minutes looking, I'm sure you can find better deals and better hardware for the $$$.
You'd have another $180 to dig up a better motherboard & 1/2 decent case and possibly get a bundled power supply.
Technically your HP OS is tied to the motherboard, but if your upgrade your OS to the SSD first, add the new HDD, keep your old HDD (lol) add your new video card and ram .... it's still the same computer :iagree:
Then if you get a new case & mobo, and move your HDD's, Optical drive, CPU + heatsink, Video card & ram to the new case & mobo.... you can argue it's still the same computer :iagree:
And then you can also try overclocking your CPU, although I'm not convinced that AMD's athlon 2's overclock particularly well - google overclocking & your CPU model.
But seriously, you could build yourself a beast with a new DDR3 Mobo with 8GB of DDR3 ram, keeping your current CPU