Window problems

I have a 1997 Mitsubishi Eclipse GS and I have a problem with both my passenger and driver doors. When the windows are down and you close the door, the window rattles a lot. I mean even if your driving down the road with em down you can hear them wiggling in there. Is there any simple way to tighten something to make it stop being soo loose? I'm totally new to cars and I need a non-technical explaination. Any help is appreciated.

They should be held firmly in the rails, even when wound down.
If they are rattling then either rails are loose, or the liftin mechanism is loose.
Only removeing the door panel will tell you.

But, you might want to check in the Eclipse forum, theres a lot of eclipse owners here, and a wealth of knowledge to go with them.

if no mechanisims are loose which would be rare, try coating the rails with some thin foam to decrease rattling