Hey guys, it's been quite a mystery how to backup battlefield 3, I found a working solution. (test on Windows 7 64-bit)
Step 1 # Open regedit > go to  "HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\EA Games\Battlefield 3" > right click > Export > save as bf3.reg
Step 2 # Navigate to your origin games directory.
Step 3 # Copy the battefield 3 folder to your backup location.
Step 4 # Install Origin on the new PC.
Step 5 # Copy the backup back into your Origin games folder.
Step 6 # Run the registry file and add to registry.

Open Origin, it will say preparing for a while until the process completes checking the files.

example data on bf3.reg
Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\EA Games]

[HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\EA Games\Battlefield 3]
"GDFBinary"="C:\\Program Files (x86)\\Origin Games\\Battlefield 3\\GDFBinary_en_US.dll"
"GameExplorer"="{16DD7F7E-2EE1-4BD6-8008-FC2DB292220F}"
"DisplayName"="Battlefield 3™"
"Locale"="en_US"
"Product GUID"="{78225C16-4123-488A-BCE3-C83DC933C9CF}"
"Install Dir"="C:\\Program Files (x86)\\Origin Games\\Battlefield 3\\"

original posting and credit to BF3 Backup

guys, any chance to recover my gamefiles so that i no need to re-download the whole 20gb file again?

just re-format my pc now

take from your friend. boss, apasal boleh forget bf3

guys, any chance to recover my gamefiles so that i no need to re-download the whole 20gb file again?

just re-format my pc now

Copy from others lol.

No other way

but the ori file still in my hdd

Then copy the file to C:\Program Files (x86)\Origin Games and then open Origin > right click at BF3 icon > download.

It should proceed to read the file and continue to installation.

IDK why. ea still downloading my game although i copied the entire folder to the directory
*sigh..

Stop the download, quit Origin, start Origin back, right click on BF3, click Repair Install.

cancelled the download,
and follow as u said
but nothing about repair install..
maybe im missing something?

You sure you paste the old files into the BF3 folder?

yup.
ive done this on steam, all works.
really dissapointed for origin.

now at home downloading the whole 20gb game @ 60% since last night.
perhaps i can back to action soon

dont know why, seems my hhd space no effect. maybe origin overwrite my previous bf3 already.

thanks mr docter

1. Copy the game folder "Battlefield 3" from Origin <install path>\Origin Games\Battlefield 3
2. On the machine that doesn't have BF3 installed start the download and pause it immediately (when it gets to 0.01%), this will give origin a chance to create the folder on your computer.
3. Replace the "Battlefield 3" folder with the one you copied.
4. Resume installation, if everything is right, it should jump to 99% and download a couple of things and you're done!

this is the best

    good one!

c easy i tell u... normal download install, pause, copy paste then resume , finally a very fast solution to setup the whole game

faster setup = faster seat bucket = faster kill = faster colonel LVL100 ha aha h ahahah