How to Sysprep a Windows Vista, 7, or 8 Image More Than Three Times
The easy way to get around the three time limit of sysprepping is to either a) use a virtual machine and save a snapshot before the first time you sysprep, or b) capture an image through the console of the state before sysprepping, and then deploy it when it to the same class machine when it needs updated. If you accidentally reached the three rearm limit without having to start over from scratch, here is a step by step how to get around it.
1) Open up Registry Editor. (Start > Run > regedit)
2) Browse to HKEY_LOCAL_MACHINE\System\Setup\Status\Sysprep Status.
3) Change the value of CleanupState to 2. (0x00000002)
4) Change the value of GeneralizationState to 7. (0x00000007)
5) Browse to HKEY_LOCAL_MACHINE\Software\Microsoft\WindowsNT\CurrentVersion\SoftwareProtectionPlatform.
6) Change the value of SkipRearm to 1. (0x00000001)
7) Open an administrative command prompt. (Start > Run > cmd... right click on the cmd icon and go to Run as Administrator)
8) Type msdtc -uninstall and push enter. Wait a minute and reboot.
9) Type msdtc -install and push enter. Wait a minute and reboot.
10) Browse to c:\windows\system32\sysprep. Delete the panther folder.
11) Run sysprep. It should now complete, and you can capture the image.
This will have to be done every time you capture the image, but it still is less time consuming than starting over from scratch.