Help!Operating system not foun

Please kindly help me, I don't know what to do-- I'm using public computer, can't type Chinese.

I turned on computer - black screen with "operating system not found"

It's a Sony Laptop, PCG 531A with WinMe, I installed WinXP 2 years ago.

Can I just use WinXP startup disk to re-start?
Or should I copy harddrive data first?
I tried to open, but can not get the hard drive out. Sony structure is strange, hard to open.

Kindly advice, really appreciate.