Why are using USB? The Sony DCR-HC30 is a minDV so it has firewire, please use that instead.
When you export the video back to tape are you doing some sort of compression? or maybe you are starting your project in the editing suite with the wrong settings? The whole idea behind digital is that you do not lose quality because you are passing 1's and 0's.
If you want something simple and FREE, check out Microsoft Movie Maker II http://www.microsoft.com/windowsxp/downloads/updates/moviemaker2.mspx
Does Adobe do the same thing? NO and neither should any other editing suite.