Okay, I'm dredging my memory on this and I'm sure someone else will be able to provide more help, but...
When the Mac starts, do you see a lot of icons appear, one at a time, across the bottom of the start screen? If so, each of those represents an extension to the OS that is being loaded. You might want to use the Control Panel and the extensions manager (I might be misremembering the name) to turn off some of them to see if it boots faster.
I remember that the manager lets you make backups of your settings, so you might want to do that first, in case you turn off something you need.