That is the easiest computer to work on ever.
You have already removed the PSU, now remove the graphics card. Get rid of case dust, install the new PSU, then install the graphics card. Install drivers. Done.
I've actually haven't removed it. the picture on page one was just one I pulled of the internet, ebay I think. but will that 500w cause problems down the road if I want to upgrade the card again? I'd hate to have to buy another PSU in 12 months if I decided to upgrade again.
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