Exchange 5.5 and Drive Space

I am running Exchange 5.5 on Windows NT Server 4.

This is a system I inherited, and I have discovered that there is virtually no room left on the hard drive due to the MDBData file being close to 3GB. The drive is a 6GB drive, and this file resides on an extended partition. Is there anyway that I can safely decrease the size of this file and not disrupt anything? I am a newbie to Exchange and would appreciate any help you may be able to provide. Thank you in advance.