Ghost 15 Back up files

Hi,

I bought Ghost 15 in Nov 2009 and every day it performs an incremental full system backup.

 

The problem is that I now have over a hundred files on my backup drive and I don't know which ones I need to keep.

They all look like this:

 

ComputerName_C_Drive001.v2i

ComputerName_C_Drive001_i001.iv2i

ComputerName_C_Drive001_i002.iv2i

 

and so on...

and  I've noticed that on the fist day of each month the numbers change. for example:

 

ComputerName_C_Drive002.v2i

ComputerName_C_Drive002_i001.iv2i

ComputerName_C_Drive002_i002.iv2i

 

Please help! My disk is getting full !!