Depending on what games you've got it will do a few things.

1.If you have NEVER downloaded a patch or map pack or add-on, then nothing will happen.
2. If you HAVE, then you will not be able to access them.

Eg. I download the map packs and patch for R:FOM. I delete all R:FOM for my game data utility. I won't be able to play online now because I don't have the patch.

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