Do you have a third party program such as a mail alert? That can cause it.
Otherwise, reboot, open OE and compact before doing anything else.

If it still gets stuck, grab the blue bar on the top of the error box and
drag it out of the way. You should be able to see the folder it is stuck on.

If it is the Folders File, open the message store and with OE *closed*
delete Folders.dbx. Note that by doing this, your subfolders will be out in
the open, but you can easily drag them back to where they were.

Your message store location:

Tools | Options | Maintenance | Store Folder will reveal the location of
your Outlook Express files. Press the Tab key to highlight the folder
location, then Ctrl+C. Close OE, then Start | Run | Ctrl+V will put the
location in the box - Click OK and you'll see the OE files. Otherwise, write
the location down and navigate to it in Windows Explorer.

In WinXP, Win2K & Win2K3, the OE user files (DBX and WAB) are by default
marked as hidden. To view these files in Windows Explorer, you must enable
Show Hidden Files and Folders under Start | Control Panel | Folder Options
Icon | View, or in Windows Explorer | Tools | Folder Options | View.
--
Bruce Hagen
MS-MVP Outlook Express
Imperial Beach, CA

"sheana" wrote in message
...
Hi, I'm trying to compact my OE. I go offline, collapse the message
"tree"
so "local folders" only is highligted. Then I hit "File --Folder--Compact
all
folders".

Compacting is almost completed and then when it tries to compact the
"folders" it stops with a red x (I think) and the message " can't
....folder
in use"

I do have a lot of folders, but it always worked before. Please help.
Thanks
in advance.