it....died? that happened to me once
your gonna need to get a new harddrive.
well thats what I had to do..
You should read.
After six years I think ditching the PSU is a fine deal. What is the GPU? I'd only sell it if it's going to still be worth a significant amount, because otherwise it might just be better to find a use for it (or keep it until there is greater need to replace it-- considering the GPU is probably the most easily replaceable part I don't see any downside in waiting on that one)
I'd make a recommendation on CPU's and stuff but I realized that I don't actually keep up with hardware news anymore. Someone else can probably give you a more informed recommendation.