8GB Memory Stick PRO Duo

Dear all, 

Recently i just bought a SanDisk 8GB Memory Stick ProDuo. I wanted to use it for my PSP 1000.

Everything seems fine as i am able to format it using my PSP, but however, i cannot put video and ISO files into it as it shows error and hang my com.

I have a  SanDisk 4GB Memory Stick ProDuo for 5 yrs now and is working prefectly fine.

please help me with it. Any advise???