You'll have to reinstall the game. It won't work like that because the registry entries that were installed when you originally installed the game would have been wiped out when you formatted the OS partition. If you wanted to save yourself from hours and hours of updating, and losing your macros and settings, here's what you can do:
Note that I'm assuming a few things for use as an example, I'm sure there will be differences in your system/hardware/software
First thing you'll need to do is backup your C:\PlayOnline folder to another Hard Drive or another computer. Or to DVD if you can burn them, I think the folder is close to 3Gb. Then you can wipe your system out and partition it.
When you have everything back up and running, (Assuming that Windows is installed on C:\ and PlayOnline is installed on D:\) here's what you need to do. Get that copy of the PlayOnline folder you made a backup of before you wiped your drive. Copy that PlayOnline folder over top of the current folder, replacing all files and folders when you do.
When that's done, start POL, then have it check all your files for you, to make sure there is no corrupt or missing files. Log into POL, and it may contact the server to check for updates, I don't remember if it did when I did it or not. Either way, you'll only have to wait for it to verify your files before you can play, and all your game sttings and macros will have been saved.
Hope that helped. ^^