One thing that stands out for me is the use of externals and a main drive. Neither are optimal. Ideally you want a minimum of three internal drives, with five being a better basic arrangement.
1st, while it MAY work, Vista is not a supported version of Windows
2nd, 3gig of ram is barely enough to load Vista and the program, with virtually nothing left over to actually DO anything
3rd, DSLR video requires a STRONG computer... your configuration really is not very strong
This message has a really good graphic about requirements - http://forums.adobe.com/thread/810750 - click the picture to enlarge to readable size