1) As J_E_D_70 indicated the first thing want to do is to try to backup all of the files you have generated. This means that the MBR and partitions and FAT must be healthy.
2) Download UBCD and check your HDD for problems, See:http://www.ultimatebootcd.com/
If above is successfull, then I would first try to use an upgrade method to re-install windows. this woulld retain your progrqms, favorite and emails. Basically it only re-writes windows files.
If Upgrade method does not work, then a complete re-install would be required.