Time Machine Disk Full?????

Hi all,
I have a problem any time my time machine go to do a backup I get a pop up box saying the disk is full? I am using a 600 GB external drive, as the time machine. I checked the info on it and it has only 101 GB left. Do's time machine copy every or just the new stuff on the mac? as i have only use 240 GB on the mac HD. Some advice would be helpful

Thanks

Shark

It will progressively overwrite the oldest data on the disk.

John T said:

It will progressively overwrite the oldest data on the disk.

Click to expand...

Why is it saying that the disc is full?

shark

are you sure its 101 GB left, not 101 MB?