Help picking out a new MB

I'm new here so sorry if i don't do something right:
I have an emachines t5048. It has the original everything except RAM, OS, and graphics card. I would like to install a new processor and it looks like i have to install a new MB as well to get anything better. I'm trying to run iTunes and games better without lagging and right now it's a problem. What would be a good option for both MB and CPU to upgrade to. Exactly what i need to get would be appreciated, like if i need a new power supply, etc.
The upgraded ram in the same kind, just 2.0gb now.
The OS is Windows 7 Ultimate.
And the graphics card is an ATI Radeon HD 4350.

you can find the original system specs here: http://www.emachines.com/products/products.html?prod=T5048

Is the memory still PC3200 or did you get something different when you upgraded it?

it's still 3200

Meh. You have a LGA 775 board. There are plenty of good 775 chips still. I think an E6700 Wolfdale will go into that board and give you a lot more speed.

Does anyone else see a reason why an E6700 wouldn't go into that board?

I'll look into the compatibility more after I make dinner.

I'm honestly not sure if your memory is fast enough for an E6700 Wolfdale.

okay, well what would work? i've never done anything major like this so i don't really know what i'm looking for. One of the reasons i need to upgrade is because it can't handle playing videos in itunes. even sd. It'll play them until like 8 seconds, freeze, and then restart the video at 13 seconds. I've messed with all sorts of settings and nothing works. The cpu is at 97-100% when this happens so i figure that's the problem.

You have a pentium 4 that's pretty quick for a single core. I think your problem isn't the CPU but rather software/firmware related. Can you play video in WMP? How about a flash video streamed from the internet?

Also, what process is actually taking up the CPU usage during playback?

well first off the problem is only in iTunes, all other programs play the video just fine. On the apple website where you download itunes, it says a dual core is required for HD video, but says a single core is fine for SD. I can't tell what the process that is causing it do to it freezing for that short period. It only stays at the high % during the freeze. (i can tell because i have the desktop gadget that shows cpu %) After that it goes down to roughly 34-41% during the remainder of the video. I don't know what else it could be. This is a brand new video card with 1gb of ram, so i don't really think that is the issue.

Well iTunes uses codecs from Quicktime so you might want to make sure that you have the latest version of Quicktime installed. You also might want to try video playback using Quicktime to see if it produces the same effect as iTunes.

I don't think it's your video card but rather I think it's software related.

What version of iTunes do you have installed?

EDIT: If both your iTunes and Quicktime are up to date then uninstall Quicktime ( leaving iTunes installed ) then re download Quicktime from Apple's site and install it.

both itunes and quicktime have been reinstalled. quicktime plays videos fine, it's just itunes. again, i think it's the cpu, so recommendations on that would be appreciated.