ProCoder is not known for its speed. Good quality, but not as fast as HCenc or CCE, probably faster than TMPGenc.
On my Core2Duo machine I can convert an avi that size in about 40 minutes or maybe slightly less.
If your machine is that slow, you will probably need to upgrade hardware for encoding tasks. In the meantime, try the Fast Mpeg encoding setting in ProCoder. Or use HCenc in FAVC. The Quenc encoder that is included with FAVC is supposedly faster than HC, but at a slight cost to quality in output.
Nothing matches CCE for speed, but it is outrageously expensive and not particularly easy to use. CCE Basic is reasonably priced, and just as fast, but only allows two passes of encoding…not a problem for me or most people. Just never liked the interface.