Quicktime loads as if buffering for ages, very slowly?

Is there any way of speeding this up?

If you are opening (cacheing) an online movie to the local QT Player, then you may have a poor ISP connection or other internet access problem. If opening (loading) a file on your local hard drive, then you may have a hard drive that has bad sectors and has to read the data multiple times or is about to fail. In the former case, try a different ISP and in the latter, run the Disk Utility and see if repairing the drive helps.

These are videos from a DVD playing through my superdrive, and not full screen either.

If using the QT Player to play "muxed" MPEG-2/VOB files, then the entire file must be read/traced by the QT Player before playback can begin. Further, the containers involved will limit content to a max of 4 GBs. In this case, you might do better to use the DVD Player or Front Row Player for playback which should avoid these two problems.

This does not, however, apply to AVI files. If the AVI files are playing back directly from the DVD, the they may be subject to packaging problems. Most content written to optical media playback is packaged to deliver data in a continuous even flow from the disc to the player. If your files were not encoded specifically for such playback, then you should copy the files from the disc to you local hard drive before attempting to play the content since the typical hard drive has a much higher throughput capability to the player.