100MB should be enough (using 320*640 resolution) for a video recorded from Movie Maker. But for Nero, if you're not going to burn direct to DVD you'll need around 4-5GB of space for the disc image.
How will it affect transfer? I don't know. But a 4 pin will work, that's what I've got.
Movie maker is alright for making videos. If your CPU is at least 1.7GHz you can use MM2 which is meant to be better.
You'll need Nero 6 to burn to a DVD and also the WMA plugin.
It may work better on your laptop, but on mine it is terrible and I have to turn off the video preview and clip making to improve the video. My laptop has 1.1GB Celeron CPU and 512 Ram and uses 4 Pin firewire. If you can manage to transfer the video to your PC without the video pausing, appearing dark or with delay, then please reply in this thread saying so, because I'm not sure whether I should consider installing firewire on a faster computer to transfer my miniDV.