I think what you are saying is that your system is rebooting and not finding your windows installation on you hard drive. This either means that your windows installation has gone or your hardrive has.
You could try putting a windows disk in and seeing if you can install it again, but i think it is more likely your harddrive has gone. In that case you will need to get someone to fit a new one. It might be best to go to a local pc shop...
This "it actually means it cannot find any harddrive" is actually not completly correct. It could just be that the MBR has been corrupted/wiped/damaged therefore the HDD is still functioning. Less of a chance, yes true but still a posibility. Even if the HDD has gone, what the system is not finding is the MBR not the actual HDD, so infact "it actually means it cannot find any harddrive" is not correct.