If I uninstall Crysis 2 from my computer completely and reinstall it, will I lose all of my data in both single and multiplayer modes?

Since single player mode isn't something they would store online, not backing them up would wipe your singleplayer saves yes. Multiplayer? Hmm, I'm not sure. But knowing how this game has turned out I wouldn't chance it.

Is there a reason you're reinstalling the game?

Since single player mode isn't something they would store online, not backing them up would wipe your singleplayer saves yes. Multiplayer? Hmm, I'm not sure. But knowing how this game has turned out I wouldn't chance it.

Is there a reason you're reinstalling the game?
Thinking about reinstalling my computer because it's starting to load things slower and I just hate that. Reforming fixes everything!

Save your local data, for SP obviously, but for MP too. Your loadouts and browser preferences are stored locally, as well as a strangely interlinked bunch of things relating to unlocks and assessments. You definitely cant just go to a new machine, login into MP, and be where you were. Much will be haywire. Guaranteed.

I'm convinced that alot of the "I lost achievements!" bugs stem from this very iffy database backend. If you create a new SP profile it affects your MP!

If you are going to reformat, be sure to deactivate your current Crysis 2 install first (use the activation.exe app in your main Crysis2 directory).

You will lose SP data, but not MP... You just have to remember your login details...