Right now, I am double checking to make sure that everything I care about is backed up from this harddrive.
I took Odeon's advice and I intend to replace the problem-prone ATI graphics card with an nVidia card.
Get a 9xxx card. I'm running a 9600GT now and it's terrific. I didn't dare to go for a 9800 since the Linux drivers just updated to include the 9600. 98 would have been dodgy.
This install of Windows XP is only about three months old, but something is seriously wrong and it's not just the corrupt drivers for the vid card. I am also getting occasional, "Disk 0/Master not detected" or "Disk 0/Master failed to respond to paging operation" (my system disk designation) and "NTFS not readable" (WTF?!?) error logs.
I bought a 500GB internal yesterday, also.
Was the drive new when you installed Windows XP? Did you format it? It sounds like an older NTFS was on it, and the MBR wasn't updated properly.
It wasn't a new drive, but I did format it. The first time I installed WinXP on this particular Maxtor drive, there was a tiny ten or twelve KB partition on it from the factory and I removed it before I formatted the drive for the first time. No problems with that install - it worked OK for over a year. I am fairly sure that this drive is beginning to fail.

Oh, I forgot to mention ...
I have already bought the nVidia GeForce 8800 GS. I looked around and it seemed a good "bang for the buck" alternative to "The Best" at sixty four bucks for a 512MB model.
I'll let those with fat pockets buy the "best" while I slink around with a compromise. This box is just for the net. If I bought the crossfire, quad processor models, I would put it on my graphics box, anyway and the kewliisssh operating system to make it dance would have to be scammed somehow. (I have one but I don't have a box to put it in)