A:yoavdothan has given you the best answer.
But if you aren't willing to d/l the 2 GB and sort it afterwards, maybe there's another thing I can suggest - searching only in your "has attachment" emails. This requires that you use Firefox and the Greasemonkey extension (VERY recommended!) and download this - http://persistent.info/archives/2005/03/01/gmail-searches
After that you can just delete all the biggest email attachments that you don't need.
Hope this somehow helps.
