Boot problem

When I switch on my computer this morning, I got this message and couldn’t boot up Windows(95):
SDRAM at Bank # :2
Searching for boot record from floppy..not found
Searching for boot record from IDE-0..ok

Invalid system disk
Replace the disk,and then press any key.

Have no problem booting from Win95 boot disk.
But couldn’t boot up Windows.

Please help!

Thank you.