Render times keep getting longer

I have noticed over the past several months that my render times keep getting longer and longer. Can anyone tell me why and how to get back to shorter render times? My settings haven't changed since I started. I am using dv footage and the project is set to NTSC-dv.
Screen redraws have also gotten much longer. The "Preparing to display video" dialog used to be just a flash, now it can take up to 30 seconds for the "thermometer" to finish.
FCP5 OS 10.4.11

How full is your harddrive?

The system drive, or the raid that the media is on?