Hi,
fallow the below steps while delete the master data.
RSA1 --> find your Info object --> right click --> maintain master data
Select rows you want to delete and click 'Delete' icon. Then SAVE.
If system prompt you message "some master data cannot be deleted"
Then goto tcode SLG1 --> enter Object: RSDMD and Subobject: MD_DEL and User: your userID and press F8.
In the next screen Expand node and double click 'Problem class additional information'
This will give you which ever objects using SIDs of this master data.
You should delete this SID according to that list.
find the below doc.
http://scn.sap.com/docs/DOC-39857