Graphics card upgrade suggestionsFollow

You have a 700 watt power supply in that machine, so you can really put any of the top end cards in it without a problem, or anything in between. Really depends on your budget and the sweet spot of price vs performance. You do only have a core 2 processor in there, so you aren't going to get a huge improvement with going with a top end card, because the video isn't going to be your bottleneck at that point. I'd start with somethign around this end: http://www.newegg.ca/Product/Product.aspx?Item=N82E16814130826 and see how that fits your budget.

What you describe is probably the card, but it could also be the monitor screen backlight capacitor starting to go out, so be prepared to also look at upgrading a monitor if this doesn't work.

You'll want to think about a motherboard processor ram swap at some point in the near future too if you do alot of gaming in general. Even a lower end Core I5 processor is going to have a bunch more horespower than your average core 2 processor, plus the ddr3 ram speed boost, etc. Just for budgeting assuming you can do the swap yourself, you're looking at probably around $300ish to swap the ram processor and motherboard, on top of the video when you start looking at that. Your power supply is fine, the hard drive is adequate but going with a solid state drive would also be something to think about eventyally.

Worst case, if it is the monitor, would be one of the main capacitors going out. If you can find someone who can soldier and is comfortable working around some voltage (or a TV repair shop) swapping them out for new capacitors shouldn't be too traumatic. On the smaller monitors its just not worth the risk.

it's basically a newer version of the same card in the link.