I assume this is the reason why if you send a file while talking to someone on skype, it sends at a miserably slow speed, i.e. bytes per second, but if you put the call on hold it does a good job of using up all your upload bandwidth?
http://www.osx86project.org/ Figure out your exact hardware and then look it up here. There isn't much hardware difference in 10.5 -> 10.6 but it's likely that your hardware is supported in Leopard, just not out of the box. If you find the iPC 0Sx86 10.5.6 image it is loaded with a shit ton of drivers installable with the OS. Here are the installation options: http://pcwizcomputer.com/ipcosx86/wp-content/uploads/2008/12/ipcppf5packagelist.png