Need help upgrading my processor.

Normally I'm good with this stuff, but I need some help this time. So basically I bought my current PC about 8 months back. It's a Compaq and the only reason I bought it is I'm good at adding in parts afterwards, but not so good at building PCs from scratch (they tend to turn in to a waste of money because i mess stuff up...) This PC came with a 3.2 GHz P4, a gig of RAM, and an integrated graphics card. It now has a Pentium D 3.0 GHz, 4 gigs of RAM, and an 8800 GS overclocked. Up until now this PC has been working out for me, but within the past few months I have been running in to problems maxing out games. The way I see it my RAM is fine and my video card is pretty good (I'll probably upgrade it in a few months). Which leaves me with my processor. It is a dual core, but from what I hear it is a bad one (the Pentium D series that is). So I'm looking to buy a Quad Core or a very good Dual Core. Last time I hunted down a processor for this PC I found out the mother board for it is very strict on what will work and what won't. The only info I can give is my PC's model number and my socket type. Hopefully someone can go further after that.

Model number: Compaq Presario PC SR5030NX

Socket Type: LGA 775

So if anyone can find me a good Dual Core or Quad Core for this PC that would be great. If not maybe you can find a new motherboard for me so I don't have to worry about these compatibility issues anymore.