How to reinstall Darwin Bootloader?

Hi guys, I recently made 2 hackintoshes. now i was trying to get the AMD kernel for my hp in my office, but i ran into a little trouble. 2 days ago, i backed up my mac with time machine. anyway, i was messing around with it, and i guess it thought my mac was a hackintosh, and it came with that nice wonderful welcome screen movie when u first get ur mac when i logged out. I had typed up a letter to a pen pal for school earlier, and hadnt backed up since before that letter. so i went into my windows 7 partition, and i tried to access my files from there, but when i went into macintosh hd, users, my account, it said there werent any files. now this means that this hackintosh kernel deleted my mac account. anyway i booted from the disk and it took an extremely long time to boot, and it take an extremely long time to boot into macintosh hd. now if any of you are familiar with reinstalling the windows bootloader on a pc using vista or 7, then you might be able to relate. i kinda need the mac version of that boot into disk go to command prompt and type
bootrec /fixmbr
bootrec /fixboot
to reinstall the Darwin Bootloader. If you guys could please help me out here, it would be so much appreciated as it takes like 3 minutes to get off the apple logo, and before it took like 30 seconds. Thanks in advance!

 

ok guys now i have an even bigger problem!!! i restored from a backup, but now its deleting my password and my account, and when i log off its still doing this! i dont know what to do! im going to try to reinstall sl then pull off the files and apps from there and hopefully this will work, if not then apple get ready to be sued.