There are two settings related to drive space in
Security Monitor Pro - the temporary working drive and the recordings drive. It sounds like you are using the default settings.
Make sure the temporary drive has adequate storage space, a minimum of 1GB is required. You can check the 'Temporary Working Folder' you are using by clicking Tools >> Application Settings >> Advanced. If drive is full, click on the Browse button to select a drive and folder that has more space. See this page for an illustrated example of
selecting the temporary folder.