Most of my captures are from analog video, either vhs or Hi8 from a sony Hi8 camcorder. I have plenty of memory on the computer although both hard drives (120/250 gb) are roughly 3/4 full, all with video. And I have about 16 single layer data disc dvd's of raw video capture files. This is so I can save the complete raw captures for a later possible use without having them take valuable hard drive space. I use a custom assembled computer that was designed specifically and exclusively for video editing. I don't use it for anything else, it doesn't even have an internet connection. I don't know what you mean by LEAVE THE COMPUTER ALONE, you mean don't open up any other applications or programs? Like I said there's nothing else to do with it.
When you mentioned to have plenty of hard drive space, why is that? I mean sure you need enough to store the video you're capturing but is there a further advantage to having hard drive space well beyond what you need? Would a computer with a less full harddrive perform better such as not drop so many frames or resample slow motion much better? It does seem that it has gradually dropped more and more frames recently so this would make sense.