You might be able to fix it yourself with the help of the
Vista Forums. Post your question to see if you can get some assistance. But if you do not know your way around computers to a minimal level it might be better to just take it to the shop, it is possible to make things worse if you do something
you're not supposed to. Tell them that you need to save some files that are on the hard drive before reinstalling. If they are reputable, they should be able to do that.
And the reason that you have to pay is the same as if your car wouldn't start because the water pump is cracked and leaking. You bought it new on the car but now it's broken. People do not work for free; we all need to eat. It is not fair
to expect people to fix computers at no cost just because the product is not tangible. Backing up data and reinstalling an operating system can take several man-hours...why should the store just absorb that cost? "Fix a booting file" is akin
to saying "We need you to make it go" when talking about a car (or spaceship) that does not run. Show me any mechanic who will say "OK I'll do that for free."
Also this should help to drive home the importance of backing up important files to an outside location. Be it a CD, a USB drive, the cloud or another hard disk, the value of a functioning backup cannot be stressed enough.
