Provisioning - New C:\ keeps changing drive letters

Hi

I have a big of a straonge issue since upgrading to 9.5 Sp1.

When we provision, the WinPE image is M, now after the image is  deployed, if i run diskpat and look at the volumes on some machine the new C is N, and on other it is N.

I do not know why it does this.

Of course the issue is that the sysprep has to be pushed to a drive letter and It fails on half the machines.

Can anyone help?