Time machine problem

Hi,
I am having a problem with the time machine. I have around 200gb data in my Macbook and everytime I back up with my time machine it keeps adding nearly 30gb information, though I have no idea where from it adds all that information. The upshot is that after only 5 back ups my 1TB hard disk is almost full. I thought that time machine backs up only those data that are added newly. Can someone help me with this?? I can't understand how and why so much data is being added everytime.

If you have one of the various Windows emulators (Parallels, VMWare, et al) then the problem is that it is noticing that the Windows "file" changes (a lot!) and backs it up faithfully each time.

Add the file to the "excluded" list in Time Machine so it is ignored.

I got that .Thank you.