G Drive

which program are you using to render with and which drive are you asving to if you are saving out to the external drive this will be slow as the usb is about 1.4 mbs - 2 mbs I would sugest that you move all none essential files to external drive and create a floder in the main c drive called my movies or divx avi if you are converting to divx file format and have your capture files in a folder called Capture on c: drive I do large files myself raging to full dvd form and vcd and the converting time is long but I use pinnacle studio I've been using this software for 3 - 4 years now and no problems on time going to main c: drive.
make sure you have at least 5-6 gig spare on c: drive for cache disable any non needed progrems and use a good program to cache your hard drive
for editing program. the g drive is proberley shutting down or your usb drivers need re-installing.
good luck on problem