i don't want to pay for having my computer repaired

just make sure you know what you are doing before formatting or remove any hardware because you can void the warranty. Try to format first but you will lose everything without a backup.

Well you can either try to roll back your system. Win7 has a tool like it. If you can't boot and you can't roll back then you can either take out your hard drive and load it in another pc so you can erase some files so your OS has the space it needs to boot properly, or you can install an OS (like linux) on a flash drive to boot from there and then you can delete some files from there too. You should always keep some space in your main hard drive so it can boot properly and perform good. Good luck with it.

Well hopefully you havent stored too many personal items on your computer or at least backed it up so you still have access to your pictures etc... My best reccomendation is to reload your opperating system... That is one of the first things you need to learn to do... You also should be aware that saving all important pictures etc on to a disk is very important... Let me know how it goes...

If you use XP you can put your installer CD and boot from CD. Then choose 'Recovery Console'. After you get C: type 'fixmbr' < enter > and 'fixboot' < enter > After type those two commands, restart your PC and see if it can boot. This is what i always do when i'm unable to boot my XP. I hope after doing that you can boot your pc.