Mac unzips my files automatically and tosses the zip in the trash as soon as that's done. Zip files are quite prone to corrupting and really aren't worth keeping. Make a regular habit of backing your actual files up somewhere. Whether it's an extra EHD (they're so cheap now) or burned on to DVDs. As soon as my purchases are downloaded, I immediately save them to two separate EHDs.
And those of you who are saying "I really need to back up"... for goodness sake,
do it! Ever notice all the people who start threads about their computer or EHD or whatever that crashed ALWAYS say, "I kept saying I really need to back my stuff up" or "I kept meaning to back my stuff up but hadn't got around to it yet." Everything that's important to you should be in at least two places. Storage is cheap! You can't put a pricetag on lost memories that can never be retrieved! Even if it's just your stash... sure you can replace most of it, but do you really want to have to do that? Back up back up BACK UP! [/end lecture mode]