well, opposed to what other people have said, I actually have found a solution for this.
What I came up with is a program called Synergy. http://synergy2.sourceforge.net/
its completely freeware, and works on pretty much all operating systems. What it does it use one mouse and keyboard (from your desktop if you so wish) to control both computers. Its very much like an extended desktop except that you can use the resources of both computers. However it goes over network, so you would have to have your two computers networked together. the best option for this would be to just run them through a router or something, but a cross-over cable between the two computers should work too. If you get stuck on how to set up the program, just google around for some a good tutorial, or look around on their site.
However this is only if your old laptop is still functional and usable. If its still a fairly new laptop, and you don't mind using its processing power for word typing or simple tasks, along side your desktop, then it'll work great.
That is basically like running a remote desktop from the laptop to the desktop. Would be functional, but don't expect a good reaction delay between the 2. If you only do office work (Word, Excel, Internet Browsing, ...) it might be an option, but you can probably forget any kind of gaming.
You could try maybe removing the laptop's lcd, though I don't reccomend it because then you'd have to rig it, and also, you can mess things up getting them apart and back together. Not for the faint of heart.
If the two computers can't run soundly on a network together then your only option is to take apart your laptop and wire up the lcd screen to no longer take an input from the laptop's graphics card, and wire it to a vga connector in order to plug it into your 8600GTS.
There aren't cables for what you want to do. All of those are outputs, they don't receive signals.
exactly. I have never seen a laptop that can take a VGA or other signal input. Mind you that's ignoring $4000 laptops with built-in full feature TV tuners.
you might be able to find some sort of TV tuner that would work in a laptop's expansion card slot, but I highly doubt it, and even if you did, it would cost upwards of $150 if not a lot more.
You're either going to have to spend a lot of money and a long period of time researching, or you're going to have to spend a lot of time researching and then rewire your laptop's LCD, either way, it probably won't work.