Saving to 2000 Format, Massive File Size

When I save files created on LT 2008 to 2000 they increase in size massively, from 2mb to up to 25mb. If the same file is saved to 2004 format it returns to 2mb.

Any help with this would be appreciated.

Many Thanks

EDIT: Purging file, deleting layers and copying drawing to blank file makes no difference.

I wanna say that it's just the way it is. In my brain the explaination goes like this, the way that AutoCAD saves files changes from version to version and becomes better and more lean and sleaker. So when you save to an older version, it just doesn't work as good. I am sure that the actual explanation is something else, but that is how I think.

Then again, to change from 2MB to 25 MB does sound a bit too much. It could be that you have ibjects in your file that was introduced in 2004 - so the 2000-format doesn't support it.