Once it's on the web, it's out there forever...
No, it's only out there until their hard drive dies with you're info on it. The internet is other computers, similar to yours.
Unfortunately, people don't realise the importance of backup until they have been through something like this, it's a hard lesson.
It might be too late, but don't touch the hard drive, anything you do now is possibly overwriting your precious data, if you are willing to lose some of it, try a home solution, if you want a full recovery or the best possible, see a pro.
I'll add that this wasn't all your fault, it was the result of badly written software, and this is why you tick that little "I agree with everything no matter what" box before it goes on to install your software. They know how valuable your family photos are, they just don't want to know about it, and they make it quite clear they have no intention of being responsible for any damage that comes from it. You were indirectly warned in the fine print, you took some risk, and now you learned that these machines are not 100% reliable.
I'm sorry for you, but don't despair, you stand a good chance of recovering the data, it may cost though.

Mainboard: Asus P5K-Premium, CPU=Intel E6850 @ x8x450fsb 3.6ghz, RAM: 4gb PC8500 Team Dark, Video: NV8800GT, HDD: 2x1Tb Samsung F3 RAID-0 + 1Tb F3, PSU: Antec 550 Basiq, OS: Win7x64, Display: 24&