Outlook 2007: "The set of folders cannot be opened" PST has reached its maximum size

I have outlook 2007. There's a PST file that Outlook is now refusing to open. When I click on it, it says

The set of folders cannot be opened. XXXXX.pst has reached its maximum size...

Outlook is telling me to delete items from the PST. But... ah... the folder is not openable, so of course I cannot delete items.

I read up a little on this. The older Outlook datafile format supported a max size of 2gb. This file is right around 2gb - just under. And I checked, it is a Outlook 2000-2002 PST file.

How can I solve this problem?