If you could overclock (I assume you can't with a HP) it would be OK and +1 you would need a new PSU for any high end GPU in that. I would go for a new PSU 2Gb extra RAM and a 6850 on that machine or save for a new build.
I have 1 GB x 4 on Dual channel. Windows 7 64-bit, and I have a 500 watt OCZ PSU. I don't know if I need to overclock my q6600 to 3.0, it would be nice, but I don't want to spend 300+ dollars on: A new mobo, a new cpu cooler, a new case, and a new gpu.
I'm thinking of getting the 6870.
I measured my fan's sides and its about 9.5 give or take. I want to get a new fan because mine is about 4 years old, its OEM and sometimes it makes a very loud noise. I've already tried putting new thermal paste, and i've dusted it, but not much helps. Can you recommend a fan that will fit? Also, will I need to spend over 300?