HD via PC IN or DVI?

I am playing my Xbox 360 using an RGB, but want to see if I can get a HD quality picture with my current tv without having to splash out on a new one.

I have a Samsung LW26A33WX/XEU that runs at 50/60Hz. Other than RGB it has: S-Video, Scart socket and composite AV. Which all obviously only enable me to get a standard picture. However, I have been informed the DVI and PC IN sockets could enable me to get a HD quality picture when gaming. I'll briefly describe both sockets...

... DVI IN has 8 pins running across, and what seems to me to be DVI-D and not DVI-I because the little box next to the pins is just a hole with nothing across the middle?! Is my conclusion right? Furthermore, the PC IN slot has 5 pins running across it.

I have also been informed that the PC IN will accept the official Xbox 360 VGA lead. However, I know it has a white (left audio) and red (right audio) lead attached to it but my PC IN only has one audio socket?! Furthermore, my DVI IN does have white and red audio sockets, but it's DVI-D and not DVI-I. Which someone else on here informed me I have to have DVI-I to enable me to get a VGA to DVI adapter so I can get HD from the DVI IN port.

If you understand how to solve my problem I would be extremely grateful because like my title states I need expert advise! Many thanks for reading my post.

Andrew.