Yes, keeping your heatsink reasonably clear of evil dust bunnies is helpful. You can monitor your processor temperature with a variety of tools. I happen to like using the All CPU meter
sidebar gadget with Core Temp, but you could try whatever monitoring software came with your motherboard if you wanted.
If you're randomly losing colors, you may have a loose cable connection between your graphics card and your monitor, especially if you're using the obsolete analog VGA signal instead of a DVI digital signal.
Whether the connection is loose or not, you definitely need to upgrade your graphics card if you want to enjoy the latest games. I would not settle for anything less than a Radeon HD6850 ($140 -20MIR
) as a minimum for gaming, but I believe that the higher performance of the Radeon HD6870 ($160 -10MIR
) is well worth the extra $20. Radeon HD7850 ($257
) performs better and uses less power, but the price increase from the HD6870 is pretty steep. If you're a dedicated NVidia fan, then the GeForce 560Ti ($217½
) continues to be their card for mid-range gaming.
A newer graphics card could help with your streaming video, since it would unload some of the video decompression work from your CPU. My father's Phenom II X3 720 2.8 GHz CPU (like yours) doesn't perform well with full-screen streaming because the Radeon HD3870X2 graphics card in his system doesn't provide much acceleration for streaming video codecs, but the much weaker Opteron 175 2.2 GHz CPU in my mother's PC handles streaming video just fine because the Radeon HD4870 graphics card provides help with the video.
You might also want to double-check that you haven't had some disaster drop your network connection down to half duplex or 10 Mb/s and that your hard-drive hasn't somehow downgraded itself to PIO mode.
Your 2x2 GiB of DDR2 memory is sufficient for most tasks. If you find that you are running out of memory (something that the aforementioned All CPU meter can show you), then you might spend $60 to add another 2x2 GiB, but if you're not using up all that you have now, the performance increase would be small.