Slow Autocad

Hi. Why does my Acad 2005, or 2004 sometimes work very slow? Some of this
files are the size of 1 MB. Usually this happend when I explode something,
or input some object (it is not necessery block). Till this time it work
good!
I can solve this only if I open new blank file and copy/paste to a new file.
I tried to purge but it does not help!
Is it possible to find out a problem?
Sorry for my bad english.

 

When this happens in our office, it is the result of receiving a drawing
from an Architect using the Architectural Desktop software. Usually it
loads OK, but when accessing the layers dialog box it shuts down our
Autocad. If we copy and then paste to a blank drawing the slow speed is
manageable - at least the program does not shut-down.

This has been my experience - don't know the why of it. I do know that
the file size from the Arch. was over 4MB for a 1600 sq. ft. building,
one floor. After copying and pasting, the file was less than 1MB.

Wish it wasn't that way. It's a nuisance every time there is a
background change.

Janice