The footprint of OneCare is probably closer to 200 Mb to 300 Mb in use, but log files, update files and supporting files can certainly add up. If your drive is so full that 600 Mb is a major chunk of your free space, you should look at freeing up space, upgrading your hard drive, or using a different security package. If you have data files taking up lots of space, consider an external drive. You can pick up an external USB 500 Gig drive for under US$100 these days.
-steve