Films formats problems

Hi,

I'm having a problem; I recently bought an HD camcorder which films in avi. format.
All my software for editing suites on my pc doesn't work with this format so I need to convert all my files in mpeg.

I have freely downloaded some converters but they either:
- convert the file format, but lose the hd quality
- convert file, keep hd quality but watermark all the video clips with their logo
- don't covert at all.

I am searching for a program that will convert the whole clip, keep the HD aspect ratio, and not leave any impression on the converted clips.
Anyone could help me in finding such a program please?