Frequently this can be the controller for the harddrive taking a dump. Another very likely culprit is the heads in your hard drive are not lining up correctly. In the case of the controller it is a small card on your hard drive and at boot up talks to your proccessor and tells it all the important information.

It is not unusual for things to get alittle scrambled and some of that info to get thru but not enough for the system to work. In the case of the heads not lining up think of the old vinyl records and a needle. Same principle but much more precise. If the head does not line up with track 00 and sector 0 you have the same results. PC knows there is a harddrive there just can not talk to it.

Get a mac you will be happier in the long run. Yes they can run windows now.