kgdjhardman2 0 Newbie Poster

I purchased my Mac G5 over a year ago from a guy in NJ. I live in Calgary, Alberta Canada and run a home-based graphic design business. I depend greatly on my mac system as it's my work machine. Over the past I've had it freeze off and on and now I'm having problems with it kicking me out of programs such as Flash or Motion. I backed up my complete hard drive onto an external drive which is bootable. I am prepared to replace the hard drive if necessary but wondering if it may be a software problem. Sometimes the fans will whirl, especially if I'm working with graphics. Can anybody give me some advice on this. Thanks, Glenn