XP's there, then it isn't, raw drive...?

I have a new drive and a fairly fresh install of XP with all the updates. Keep AVG antivirus on it and run that almost daily and Spybot. It's a 500 GB SATA drive that I partitioned into three, a small volume to just hold the XP CD files, another for possible page file and the rest the primary drive.

The other day, it booted up fine, I ran or started to run scan disk and it brought up the screen that Windows failed to start. I had the option of start normally, last known good, config, etc. No matter what I chose, it would cycle back to this screen. It would display a blue screen for a fraction of a second but not long enough to read.

I have an older drive that is failing but will boot up. First, the new drive primary partition didn't show up although the smaller partitions did.

I decided to clean up the old drive, update the virus def. and run it and do scandisk.

After that, I went into bios and changed the boot up disc priority from the old drive to the new drive and it started up like nothing happened. This lasted a day and then the same thing. But this time, I could see the drive new drive's primary partition. The format said raw even though I could see the files loaded on the drive. I attempted to do a scandisc on the drive, about 3/4 through it could not complete it. Ran scan disk on the old drive again and the virus checker. Nothing but a few tracking cookies.

I again change priority of boot up to the new drive and it works again like nothing happens. I don't have a lot of programs on this new drive and hadn't recently installed any new hardware other than bluetooth software about a week prior. What's going on?

I thought at first I was going to have to do a repair install but I've never experienced a computer doing this. What can I do to prevent it from happening again?