What Started this RAW?

OK I have two drives C:XPPro NTFS, and D:98SE FAT32. I use a third party dual boot program OSL2000.
The first sign of problems. I was doing a normal windows update with XP when error messages popped up and read Data was lost on the D:98 drive. I rebooted in booth drives and everything seemed normal.
Two or three days later the XP drive started making noise and wouldn't boot so I hit the reset button and it booted just fine. We began to reload XP on another hard drive and restore programs and data. That is when the problems got worse.
After we reinstalled XP we tried to open the 98 drive within XP and it prompted us to format the drive. We looked at the property's and it read that the drive format was RAW.
We then purchased Data Recovery Wizard which worked perfectly. Got all the data, reinstalled 98se. We are up and running. My question is What could have caused this to happen in the first place?
I am concerned that if it happened and I don't know what caused it than it could happen again. I was told that the computer could have been doing a checkdisk that was interrupted. I can only guess that something with the dual boot status of the computer has caused this but I don't know what.

Sounds like youre working with some fairly old hardware... could be a failing hard drive or a number of other things.

Can you please list all of your hardware...

any simple corruption of the mbr or partition table could cause it to get lost like that.
had you tried to boot into the 98 anyways?
running any of the software that will mess with partition tables and all could cause it, partition magic and tell it OK that it could "fix" something , that wasnt nessisarily wrong. or any one of the others.
even a virus, or just a minor corruption on the drive itself. Even allowing windows to do chkdsks during an Unstable situation, can get it to false trigger and try and "fix" something and make it worse.
Unstable meaning if memory was failing, of the hard drive was faultering, if an OC is to high, or even if the power anywhere in the system from PSU and down was causing problems.

Therein what King asked, what is it?