Flashing question mark can be the hard drive or the operating system.
If you have the original install disk 1 of 2 that came with your macbook and haven't added 10.5 yet, put install disk 1 or the leopard retail disk, restart and hold down "c". When you get to the grey screen with apple/spinning gear, release. It should take you to the installer window. Select utility > disk utility > if you see your hard drive volume, probably named "macintosh hd", select it and run "repair disk".
If it finds errors, it may need to have your software reinstalled.
Hope you have a backup of your data...you might want to look at advanced options for support if that is a concern.
If you don't see your hard drive, the hard drive has probably failed. If it is the hard drive, under warranty, you can have a service provider order it or you can have Apple send you a replacement one.
Either way, with disk utility, close that window, select installer, quit installer and when you get to restart, hold down option or alt key to boot to a screen that shows your install disk, then eject it.
Good luck
