It sounds like there is no operating system on the hard drive or there is a problem with the boot loader configuration. If this is the case there are quite a few possible causes.
The first thing to check is the bios:
As soon as you press the on button keep pressing the F2 key until you see a blue screen with System Info written near the top middle.
Under the system menu (which is expanded by defaut) use your arrow keys to select "Boot Sequence" and make sure that "Internal HDD" is a valid option (i.e. has a number next to it) (it doesn't have to be number one - in fact it's usally best to leave your CD/DVD drive as no. 1).
If there is anything above "Internal HDD" like a USB drive or a CD drive then ensure that you are trying to boot without any CDs or USBs in your laptop (these ususlly shouldn't cause a problem but just on the off chance that you put in something with a (now useless or broken) operating system).
Following this, if you have a windows bootable CD (or you can borrow one from a friend) you could try booting from the CD using the instructions here "http://support.microsoft.com/kb/927392"
and try "bootrec.exe /FixMbr" and "bootrec.exe /FixBoot"
then remove the windows CD and see if you can boot normally.
These steps fix problems with the bootloader configuration and, to my knowledge, are even safe to use on a perfectly good windows installation.
If this doesn't work you may have a hard drive failure on your hands or posibly some other sort of error.
If you can't get access to a windows CD then you could google about how to create a bootable linux CD (eg. ubuntu). If you can boot any operating system from a CD then that narrows the problem down to being something to do with the hard drive.
If you try any of these steps let us know how you get on and we may be able to help further. Also, you would have mentioned if anyone would have recently tried to repartition the laptops HDD or set up dual booting on it, right?