I'm having a problem with some of the files at work growing in size from simply copying objects in from another drawing.  These aren't blocks are massive amounts of line work.  I have a file that is 487kb and when i copied in some lights from another drawing, the file size grew to over 8mb. The lights were nothing more than 5 circles. I've used -purge, regapp, wblock commands all in an attempt to try and clean the file up with no avail. Also tried a lisp to clean out the layer filter. I'm stuck.  Does anyone have a suggestion or ever run across this type of issue?  Any assistance would be greatly appreciated. 

The file was created using AutoCAD. I doubt there is anything from microstation floating around in the background but i don't know how to check. I know the problem is coming from copying stuff in from another file which shouldn't cause such an issue.  I'm just completely stuck at this point.

I tried all of those things but to no avail.  I finally sorted it out though and was about to post my solution.  I ended up doing the following and it worked really well.

1.)  DXFOUT
2.) Open new DXF file and PURGE>ALL; -PURGE>REGAPPS and AUDIT.
3.) SaveAs the new DXF file as a DWG.

after I did that, My file went from &MB to around 200kb.

I had the same issue. Usually they are drawings created in Microstation. The solution is simple: delete wipeouts. deleting blocks like sinks and toilets reduced the size of my drawings significantly too ('m not sure what was so special an=bout these objects tho) 

I've seen drawings having thousands of unused linetypes that won't purge with ordinary methods. A good workaround is outlined in at the posting dated "01-14-2013 09:47 AM" at http://forums.autodesk.com/t5/AutoCAD-LT-General/Linetypes-Will-not-Purge/td-p/3236334/page/2. Autodesk's new tool to do the same task will be welcome - if it works and is documented well.