How do i Know what files are on my drive

Hi can some one please help me, I have a my world book II (white) set up as a time capsule for my mac.

I have a solid flashing light approx 0.5 sec, which according to the manual is a special event. I have found out that the drive is 95% full.

The problem is that when i originally installed the drive i think i asked either my music or photos to go to the drive as storage as well as being a time capsule.
Is there any way i can find out what i have done as i believe i might have to re format it. The other question is that i thought when it is set up a capsule it would overwrite the old files unless you have added any thing else.
I thought having a 1TB hard drive and 1TB capsule i would never be able to fill it up.

If you are using Time Machine then it should have a mirror image of your system. You can confirm by manually mapping the Time Machine share.