Why did my hardrive get wiped clean when I did a simple system update?

On May 4th, 2010 my eMac, which is running Mac OS X (10.4.11) did it's automatic system update. I bought this eMac it was a refurb from eBay. I never had a single problem, it ran perfectly fine when I had tested it out, everything was great. I transferred some photos and music from my old Windows computer to the "new" eMac, and some of the music was newer and needed a system update to work properly. I thought nothing of it so I went to www.apple.com and looked for the update, found it, and started it. I had went ahead and stepped away while it updated to pass the time. Once I had gotten back I went ahead and restarted the computer like you must do with every update, when I had logged back in, my hard drive was wiped clean. At the time I was a little perturbed to say the least, but I passed it off as it not having an update in so long that it had just, more or less, reinstalled the new system update. Once again I passed it off not thinking anything of it, never had another problem out of it at all. I had put a many of programs such as Adobe Photoshop CS3, Adobe Audition, Dreamweaber, Garageband (full version), djay v3, and I had even JUST put Logic Studio on it, and many others. After putting, more or less, my entire livelihood on the eMac, (I create website designs, various ads, freelance photography and videography, and a verity of other logos, designs, insignia, emblems, ect...) it did another automatic update, now my ENTIRE hard drive is wiped clean. I no longer have possession of my software discs due to someone stealing them along with all my audio cds, and dvds. I don't have the money to spend on new software, (altogether my software added up to just over $2.5k) and now I am already feeling the effects. What can I do? Will Apple even help?