Okay I think i'll be going for the HD5770. I was just checking the inside of the PC and thought i'd mention that it's a 650W PSU. Is that going to be okay? I would imagine so.
Additionally, will the mentioned graphics card still fit? What is its size in comparison with the 8800GTS, and is all its cabling and required slots the same? I know my main computer has a GTX260 and its the size of 2 household bricks, monster of a card physically.
Also I noticed that both the RAM Cards are 2GB and yet on My Computer Properties it only says 3GB. How bizarre... :S
32-Bit OS's only allow a address space up to 4GB.