Exchange's 2-GB limit on offline folders (OSTs) and personal folders (PSTs) has been a common cause of trouble for Exchange administrators. Folders can exceed the size limit without warning, and after a folder surpasses the limit, the folder is unusable.
However, Microsoft offers a tool that truncates oversized PST and OST files so you can recover at least some of the information in the folder. Commonly referred to as the "Crop Tool," this utility was previously available only by contacting Microsoft Product Support Services.
But Microsoft has now made this tool available via download. To obtain a copy of this tool, you can download it from Microsoft's Exchange 2000 Tool: PST2GB Web page.
Keep in mind that the Crop Tool doesn't guarantee full recovery of data. The best way to fix this problem is to avoid it altogether. For best results, set mailbox limits for users, and monitor the size of PST and OST files.