well, I am no expert on the EA downloader, but I believe once you have purchased a booster, the downloader will allow you to download that booster as many times as you want. Simply log into the EA downloader and select the booster.
Now, what I don't know about is the cached file the downloader puts on your HD. Maybe it gets deleted once you have successfully installed the booster, maybe it will still be there.
If it is still there, you should be able to install it directly from there, without downloading the whole thing again.
Remember, all the EA downloader does is download the booster and then put it in a cache folder on your system drive ( usually C ). Look for that cached folder.
Maybe someone with the same problem can confirm this. I also suggest you use the SEARCH to find threads about the same thing. I am sure this issue has been discussed here before.
moved to BF2:Help
EDIT: wtf, slayer..