Changed my ROM and now phone wont turn on like the battery is dead...?

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http://forums.androidcentral.com – So i got bored and rooted my GS3... It all went perfect and everything worked fine. Then i was looking around on the internet and came across ROMs. They looked pretty cool so i watched a YouTube video and decided to change my ROM. BAD IDEA! I downloaded the ROM did a backup and reset and then booted off the new ROM. The last step of installation was to roboot the phone. So i did and it has yet to turn back on. I have tried to get into download mode and recovery mode, ive tried charging and taking the battery out. No luck. I really hope i didnt just break this thing :( If you need to know i hav (HowTos)