Seems like your hard drive is not booting. Any problems with the system prior to this?
Generally, when you get that error ... your system is severely corrupted or your hard drive has crashed and no longer boots.
Your options at this point is to try to do a system recovery. Do you have backups of everything?
Your netbook should have a recovery partition...you can use the steps outlined in the link below to get the system back to factory defaults. All the data you have will be lost though.
Since you can't get into the recovery partition, then the only other option is to contact acer for recovery media...which would come on a CD. That means you would need an external usb cd player to read it.