Easiest thing to do is take the old hard disk and actually hook it up to your new computer. Easiest thing to achieve that is to temporarily unplug the data and power cable from the cdrom and hook that to your old hard disk. If you make sure the side of the data cable with the stripe is toward the power plug on the drive, the computer should simply see it when you boot.
Assuming the new one has a really big hard drive, you can make a folder on your new computer called "old-stuff" or something. Then copy the entire contents of the old computer's hard drive into the folder on the new one. Then you can put the disk back in your old machine and pick through/organize the stuff at your leisure.
Any programs/plugins you installed will have to be installed again, but if you saved the uninstalled plugin stuff on your old computer that should be easy enough. Media player ugrades might be a little more tricky since you almost have to be on the internet to installl that stuff.
windows programs put various stuff in your windows folder and registry so you can't simply copy folders of programs over and expect them to work. Sometimes it work most of the time it doesn't, so you basically have to re install every app you plan to use...
