Well the existance of an Ubuntu Live disk red-flags the possiblity that your Linux Grub is ultimately the source. I had this situation and had to do a completely New Install as support for XP from Linux people is non-existant in fact they will laugh in your face.
Only it's not funny...
I just re-read your post. Please pay close attention to the Recovery Console options and try it again, as you should be able to boot to this no matter how corrupt the HD software is.
If you REALLY can't get there, then I would be thinking hardware problems and not software. So then if the Ubuntu is working, that sort of indicates the hardware is GOOD, which is a pickle, for sure.
<looks for a pickle icon ...>
Hmm . . .
Okay, here's my thought.
Download & install the HD utility software for your particular HD. All the manufacturer's make this available on their web-site's Support section and run the utility to make sure the stinkin' HD is good (or find out maybe it is BAD, only Ubuntu doesn't know it yet . . .)
Also, maybe the Utility can FIX whatever is wrong.
If the HD turns out to be good, then I don't know what's next. Maybe the HD cable, the CD/DVD device or maybe even HEAT. Is your CPU fan clean & spinning really, really fast ?
Or Power Supply maybe. How old is it, what is it's wattage and is it a good one or a cheapie no-name ?
Hay ever-body ! Come help this guy; this one sounds FUN !!!
