Deleted some LaunchDaemons files and now Mac doesn't start

You will have to reinstall OS X.

Reinstall OS X without erasing the drive

Do the following:

1. Repair the Hard Drive and Permissions

Boot from your Snow Leopard Installer disc. After the installer loads select your language and click on the Continue button. When the menu bar appears select Disk Utility from the Utilities menu. After DU loads select your hard drive entry (mfgr.'s ID and drive size) from the the left side list. In the DU status area you will see an entry for the S.M.A.R.T. status of the hard drive. If it does not say "Verified" then the hard drive is failing or failed. (SMART status is not reported on external Firewire or USB drives.) If the drive is "Verified" then select your OS X volume from the list on the left (sub-entry below the drive entry,) click on the First Aid tab, then click on the Repair Disk button. If DU reports any errors that have been fixed, then re-run Repair Disk until no errors are reported. If no errors are reported click on the Repair Permissions button. Wait until the operation completes, then quit DU and return to the installer.

If DU reports errors it cannot fix, then you will need Disk Warrior and/or Tech Tool Pro to repair the drive. If you don't have either of them or if neither of them can fix the drive, then you will need to reformat the drive and reinstall OS X.

2. Reinstall Snow Leopard

If the drive is OK then quit DU and return to the installer. Proceed with reinstalling OS X. Note that the Snow Leopard installer will not erase your drive or disturb your files. After installing a fresh copy of OS X the installer will move your Home folder, third-party applications, support items, and network preferences into the newly installed system.

Download and install the Combo Updater for the version you prefer from support.apple.com/downloads/.

Nope. Reinstall is the only way. Reinstalling as outlined doesn't create another user nor take up more space. It does require about 10 GBs of free space during installation.

Start up the computer with the DVD inserted as far as it will go without forcing it. After the startup chime press and hold down the 'C' key which will cause the computer to "suck" in the DVD and begin booting from it.

Or you can boot the computer as above and hold down the 'C' key then insert the DVD into the slot.

In either case the DVD should end up in the optical drive. If it doesn't boot from the DVD, then restart and hold down the 'C' key after you hear the chime.

Macintosh HD is usually the OS X boot volume, so choose that one.

Nothing in my procedure would have erased the hard drive. How do you know everything is gone? Did you get OS X reinstalled? Are you sure you did not erase the drive on your own?

Open the Accounts preferences. How many user accounts are listed other than the Guest account? If there are two listed, then log out of the current account and log into the other account. There you should find everything.

Do you have a Home folder with your Documents, Downloads, etc. folders? Are you files there? If you click on the Desktop then select Finder Preferences from the Finder menu, then check the boxes for devices you want displayed on the Desktop. Is that what you think you are missing?