Problem Booting to NTFS Partiton in XP Prof

[Squeezy]

I have a system that has been fine for a couple of years, until last week.
Mobo: Abit KT7A Raid
IDE 1: 1 x 20gb HDD, C: (W98se) and various other partitions.
IDE2: 2 x CD/DVD drives
Raid: 1 80gb HDD one both connectors running as Raid 0 5 partitons NTFS and one FAT32

I cannot boot to any of the XP installations I have on the NTFS drives - hangs for a while after the initial XP screen, then ree-boots.
Fdisk shows all partitions but drive letters missing for the NTFS partitions.
I have tried variuos other disk recovery s/w and they all show the drives OK and the partition letters etc. Eventvwr shows the message Device not ready for access.
any ideas gratefully received.
Cheers.