I had to do a clean install of Windows XP Pro on my home computer recently and everything went just fine, but it seems that the computer will not boot up unless the Windows installation CD is the in CD-Rom drive. Nothing has changed with my computer hardware wise, and this didn’t happen when I first installed windows on this computer. I’ve tried reformatting and reinstalling but it doesn’t help. Any suggestions would be great!

I have a dell optiplex gx 260 – new hd 500gb, 2gb memory. 2 cd/dvd writers. This was working fine. I reloaded the os and then restored the data 2 months ago. 9 days ago turned on the computer, saw the dell splash screen with options of F2/12 then splash screen went off like normal and all I had was a blinking prompt in the upper left hand corner of the screen. Booted to diagnostics – all passed. Swapped power supplies. same result wouldn’t boot from hd. Reformatted hd, reloaded windows and minimum software – office, anti-virus, adobe stuff, firefox. Added users. Worked great.
Next day wouldn’t boot again. Followed same process of reformatting hd and loading os and sw. This time made ghost image. I have reloaded the ghost image 5 times and the computer runs great for a day. But it will not boot again after a day. I have even swapped hard drives.
Any idea what the problem is?
Running Windows XP SP3