Ah, an upgrade issue on a prebuilt system with a low-end PSU...Here is the basic HP5694 build: http://www.gateway.com/systems/product/529668104.php?tab=specs#techspecs
Seeing as how your PSU is 300w and your motherboard is a 780G chipset, it *should* in theory be able to use a Phenom 9950 BE, but OCing is likely out of the question, and the PSU has a pretty bad fudge factor, mainly because the 9950 BE is a good step up from the energy effecient 9100E, so it may have enough power to use the 9950 BE, but it may not, and it most likely will not have a lot of overhead if you want to install even a low-end GPU (Which you should think about, seeing as how you have intergrated graphics on you're using, that'll be the main thing to slow down the PC in games)...
So the CPU upgrade may work, but it may also require a PSU upgrade...And this is a prebuilt system, so any warranty you have will likely be voided as soon as you start messing around in it...
Adding a GPU instead of a new CPU would likely be your best bet, seeing as how you have a lower clocked quad core, but still a newer CPU, your GPU is most likely what is limiting your game performance the most (Even though the CPU is definantly a factor due to low clocks)...A 8600GT would likely be one of your better low-power GPU options, yet still have enough power to play most games decently at low settings...
Just about any upgrade in your prebuilt system will likely be a pain to do, and the PSU may have a fudge factor (Allowing certain minor upgrades), but any upgrade due to your PSU may have issues being powered, so I'd recommend being careful, and the CPU is definantly not the easiest thing to upgrade (Or RMA if the upgrade doesn't work), so I'd recommend upgrading your GPU first and seeing if the performance is improved enough that you can live with the system until you can build a new system...
I can list some GPUs which should work in your system later if you'd like...
Respectfully,
PROACEX1
To build a PC or to not build a PC, that is a stupid question...An obvious one too...
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