Make full use of your Sony camcorder video on your computer

"I recently purchased Sony's HDR-HC1 high-definition camcorder, and I found out my current computer is way too slow for HD video editing. I want to purchase a brand new PC or Mac to get the job done (since my current PC is a 6-year-old 1Ghz Athlon dinosaur). Should I stay on PC platform, or should I switch to Mac? Either way, what is the spec of the computer I should get? I appreciate your sharing of your own experience!"