Having only had a Mac since November, I've never had to upgrade the OS. Since Mountain Lion is coming out this month, or so I've heard, I'm going to want to upgrade. When I was on Windows I used to have to do a reformat, install the latest OS and then reinstall everything. Is that the case with OS X? There's some apps I have that came preloaded on my Mac - I bought it from a different supplier over Apple - and I don't have the serial numbers any more, and don't want to lose the software. How will installing Mountain Lion be?