NTLDR missing ?

Hello, I have a 4 year old Gateway 505GR desktop. It's alway been a great pc and now I don't know what's going on. A couple of times, after disconnecting from the internet but leaving my computer on, a black screen would come up and say: REBOOT OR INSERT BOOT DISK I would reboot, get the Gateway splash screen, then instead of going to windows I would get the "safe mode" screen. From which I would choose "last good configuration that worked" and then my computer would go into Windows XP and everything would be fine. Then one day I recieved the "reboot" screen again… so I thought maybe if I use my Gateway restore DVD this might help. This DVD is the only disc I recieved with my computer when I bought it new. Now I know that by using it, it will erase all my data and reload all my settings and drivers and programs back to factory. I have used this disc before and it had worked well. I'm not worried about losing any data, 'cause all the important stuff i have already saved on a disc. This is where the problem get's worse. I put the DVD in and rebooted. The Symantec Ghost 7.5 screen comes up like it should and begins to do it's thing. However the speed and the amount of data being transfered is very low… actually it seem as if nothing is really happening at all. The progress bar shows nothing being done and then I'm giving an message that says: GHOSTERR.TXT and it asked me to insert a disc that I don't have and then select "yes or no" Since after trying to run this DVD, when ever I turn my computer on, it goes to a black screen that says: NTLDR MISSING and it will not do anything else. I have never be givin the "REBOOT OR INSERT REBOOT DISC" message and I cannot get into safe mode any more. I can go to my BIOS screen when rebooting but I not sure that i'm seeing anything wrong. I've been searching the internet for the last week in my spare time on my girlfriends computer (which I'm on right now) and have been seeing lots of stuff that just doesn't seem to get me any where. Curious though, I was able to get to an A:\ prompt, but I could never get to a C:\ prompt. I believe the problem I'm having when I try to run my restore DVD is not the program or the disc itself but it's because it can't run correctly with what ever the problem is with my computer. I have kept this computer stock from the factory. The only things I have added were Windows Office (added over a year ago), Spybot and Ad-aware SE (both have been on for some time now). I have no viruses that I'm aware of. I took the side panel off and checked for loose connections and did not see anything out of the ordinary. I do not hear any "clicks or beeps" when turning the computer on or rebooting. It acts like either my hard drive isn't working right. At least this is the only idea I can come up with. I need some one to point in the right direction of what I need to look at or be looking for. Any help would be great. thanks

I would assume that this is hardware failure, maybe aggrevated by dirt, after blowing out the computer thoroughly I would boot into bios and check my temperatures and voltages. Leave the side off and make sure all fans are operating properly. Next I would check the hard drive with a utility downloaded from the manufacturer and run from a dos boot disk, in a few cases I have seen a bad cpu or bad ram cause this, they are the hardest to isolate tho? You can run memtest86 for the ram but I doubt it's the problem. If it's the cpu there's no way to really isolate that except to downclock it, I would only suspect a problem with the cpu if I saw a high temperature in bios. You could even have a bad cable.

In checking my Hardware Monitoring the temp for the processor zone is around 54 degrees C. I've checked some sites on the net and this appears to be good for my Pentium 4. I don't think I'm finding anything in the BIOS that shows my hard drive listed. Where in the BIOS does it show it? I see my DVD drive and my CD ROM drive listed. Under the boot tab if I click on Boot Device Priority it shows my DVD drive as 1st Boot Device. Shouldn't it show my Hard drive as second?

check and reseat the cables to the hard drive and check the one going to the motherboard