Try this - works most of the time -
Boot off Windows CD to recovery console. Delete the 5 registry files (system, software, sam, security and default) in c:\windows\system32\config. Copy the same 5 files from c:\windows\repair to c:\windows\system32\config (these are orig default installation files). Reboot computer and it will go into Windows. Desktop may look a little strange but don't worry that will be fixed next.
Open the System Volume Information folder C:\System Volume Information . This folder contains one or more _restore {GUID} folders such as "_restore{87BD3667-3246-476B-923F-F86E30B3E7F8}"
Open a recent dated folder (not the current one) to locate a Snapshot subfolder; eg C:\System Volume Information\_restore{D86480E3-73EF-47BC-A0EB-A81BE6EE3ED8}RP1Snapshot
Copy the following files to the C:\Windows\Temp folder
_registry_user_.default
_registry_machine_security
_registry_machine_software
_registry_machine_system
_registry_machine_sam
Reboot off Windows Cd into recovery console.
Type the following
delete c:\windows\system32\config\sam
delete c:\windows\system32\config\security
delete c:\windows\system32\config\software
delete c:\windows\system32\config\default
delete c:\windows\system32\config\system
copy c:\windows\temp\_registry_machine_software c:\windows\system32\config\software
copy c:\windows\temp\_registry_machine_system c:\windows\system32\config\system
copy c:\windows\temp\_registry_machine_sam c:\windows\system32\config\sam
copy c:\windows\temp\_registry_machine_security c:\windows\system32\config\security
copy c:\windows\temp\_registry_user_.default c:\windows\system32\config\default
Reboot to Windows. If this is not correct recovery point you can now use System Restore as normal.