I am about to upgrade from 10.3.9 Panther to 10.4 on my Mac. I do not have an external hard drive and cannot afford to buy one but I was just wondering is it safe to upgrade my OS without one? But just out of intrest, if I did do an upgrade but did back up my system to a hard drive and it went wrong, how would I put it get my system back so it was like nothing happened? And most importantly, how do I back up with a hard drive? Any software needed?