Upgrading an old computer?

for gaming you are looking at getting an intel cpu depending on your bufdget an i3 or an i5 a compatible motherboard and id say minimum gpu something like a hd6850 or a 550ti with ast least 4gb ram
what you need to do is post your budget and preferred website for parts and usually you will get great advice on what parts to buy for the best price/performance

Would it be better if I set up an entirely new parts or just stay with the old? I don't particularly have an budget, maybe about SG$1000. I would prefer going to the shop itself to get my parts, so I would prefer people recommending parts instead.

Thanks.

I visited HP site for the specifications of your motherboard at http://h20000.www2.hp.com/bizsupport/TechSupport/Docume...

Unfortunately, the upgrade path for the HP CQ3070D is limiting... the motherboard is not giving you flexible room upgrade for what I think you need playing games mid-high settings. I highly recommend you build an entirely new computer.