I may get flamed for this but I really think it can help u. Assuming your corrupted download got this far. Go look into the download directory of EA downloader. (By default: C:\Program Files\Electronic Arts\EA Downloader\cache\"YourProfileName"\)
check for file called: eagamesbf2-2006online_contentbf2-ep1.eam and open it with notepad. In that file, it says regkey = something. Well, that something is your BF2 SF cd-key. Copy it.
Ask someone u know to borrow u their cd of bf2:sf and install it entering your cd-key or (and this is the part I may get flammed for) if you don't know anyone that has it download an image of of torrentspy or something like that but once again install it with your cd-key. After all, you paid for it anyway, it's not your fault EA's products are full of bugs. If you choose to do that make sure it has a good feedback and that the file is free of adware, spyware, viruses ...