Premier Pro problems Plulling my hear out

Hi all im a PC user and im having a tuff time with Premiere Pro 5.5,I edit HDDSLR footage from a 7D and im having constant crashes and poor performance. I have read every forum and blog I could have I have did many clean installs and still nothing. Using my footage natively is worst and transcoding to avid DNxHD is better but still slow I know its a better way. Im posting my Pc specs in pics: GTX 285, SSD,raptor,core I7