To start, I made a BIG mistake. I bought an HP "Media Center computer" a few years ago. I am living with the pain of the system, and instead of trying to video edit and trying to play games, I am finally going to upgrade. I would like a new processor (would be willing to overclock)/motherboard and maybe RAM if you think it is needed. I am new to this stuff, but have decent knowledge of computers. My use of this machine is probably 40% Gaming, 40% HD Video editing and 20% school/ internet use (the basics).
Here are the specs for the machine I purchased (for a a ridiculous amount...) I already upgraded my GFX card to a 8800GT overclocked, and power supply to a Antec Earthwatts 500 watt (80 plus) power supply. I also would like to know if I should upgrade my case while I'm at it (they arent too much, and I wouldn't mind a cool one!)
My budget would be <$300 but I would be willing to pay more if it is really worth it.
Sorry if this is a lot to ask for, but there are so many options!
Do some more research on installing a new board before you invest in your hp. I also upgraded my compaq (with hp motherboard) and had no real problems installing the board and getting all the case connections to work, but I've been doing this for 17 years. I used an ecs g33 Intel chipset board. Your windows software is hp proprietary, meaning you'll have to format and reinstall windows. I used a dell oem vista dvd and reactivated windows using the old coa sticker number on the case. I actually like my compaq case, except for it's lack of a front fan. Check fatwallet or slickdeals.net for deals on cases. Shipping makes ordering cases online less enticing. I go to my local Fry's store for them.