Re-IP fails on Windows 2003/2008 servers.

Re-IP fails during a Replica failover with an error:
Info [RestoreSession] Result 'Failed', description 'The process cannot access the file because it is being used by another process'

There are several reasons that can cause the error:
[14.05.2013 12:53:00] <01> Info [RestoreSession] Result 'Failed', description 'The process cannot access the file because it is being used by another process'
However there is a known issue with 2003/2008 servers with disks that don't have a drive letter.
If this is the case, during the failover you will see the following in the logs:[

14.05.2013 12:52:52] <01> Info [ReIP] Searching SYSTEM registry hive in volume '\'.
[14.05.2013 12:52:52] <01> Info [ReIP] Creating registry hive load session.
[14.05.2013 12:52:52] <01> Error [ReIP] Volume processing is failed.
[14.05.2013 12:52:52] <01> Error The process cannot access the file because it is being used by another process (System.ComponentModel.Win32Exception)
......
[14.05.2013 12:53:00] <01> Info [RestoreSession] Result 'Failed', description 'The process cannot access the file because it is being used by another process'
[14.05.2013 12:53:00] <01> Error Re-IP process failed. Error: '{0}'.Arguments: (Veeam.Backup.Common.CRegeneratedTraceException)
[14.05.2013 12:53:00] <01> Error at Veeam.Backup.Common.CExceptionUtil.RegenTraceExc(Exception originalExc, String formatString, Object[] args)
[14.05.2013 12:53:00] <01> Error at Veeam.Backup.Core.CViReIPAlg.Failover()
[14.05.2013 12:53:00] <01> Error at Veeam.Backup.Core.CViSnapFailoverAlg.Failover()
[14.05.2013 12:53:00] <01> Error at Veeam.Backup.Core.CViPlatform.Veeam.Backup.Core.IPlatform.DoVmFailover(COib oib, CRestoreSession jobSess)
[14.05.2013 12:53:00] <01> Error at Veeam.Backup.Core.CVmReplicaFailover.Failover(CRestoreSession jobSess, CData data)
[14.05.2013 12:53:00] <01> Error The process cannot access the file because it is being used by another process (System.ComponentModel.Win32Exception)

Attempt to do a Windows File level restore of the VM. If you're able to successfully perform a File level restore and browse down to see the C:\windows folder of the VM, it is likely the known issue with Re-IP and you should contact support as there is a hotfix that can be applied.