Well after further investigation into this problem as i had it again i realised that when you have done some work in windows PE (created partitions and then assigned drive letters etc) and shut the pc down then come to use windows PE again the drive letters get reset so if you created a system partition and gave it letter S, it would be the first available letter the next time you use windows PE and this was my problem. I remember reading this somewhere in a tutorial that windows PE does this but it never clicked in my mind until now. A bit daft really. Thanks for the reply though