Is there a replacement for the old SysInternals NewSID utility that will work for Windows 7?
I found out the hard way that NewSID will totally hose a Windows 7 setup (BSOD on reboot). Apparently the same problem occurs for Windows Server 2008 R2. They've officially announced that NewSID will be retired in November, possibly because of this issue.
I'm aware of SYSPREP, but it's not a clean replacement in my case so I was hoping that there was another utility similar to NewSID that worked with Windows 7. Reworking our system to use SYSPREP will be ugly and slower as well. Is there another alternative?
You don't need NewSID. What's more, it has never been needed and the bit of code that generates a new machine SID as part of the sysprep process will ultimately be removed from sysprep in future.
See Mark Russinovich's latest blog entry: The Machine SID Duplication Myth.
Sysprep combined with an unattend file should solve most of your problems, although, as you say, it may work a bit slower since mini-setup is run after reboot. Are there any specific scenarios you need to solve using newsid or just OS generalization in general?
I wouldn't be surprised if MS knowingly crashed OSes where newsid was run. The only supported generalization teqnique is (as far as I know) sysprep, so if you're running production systems I'd stick with that.
Might not be the answer you're hoping for, though.
A new SID IS still needed in a few specific situations, as was also mentioned in Russinovich's post's comments. I'm currently having problems with six cloned clients connected to a WSUS server. Since they have identical SIDs, and aren't members of a domain, only one of them will ever show up in WSUS. The last one to connect simply replaces all the other ones.
NewSID is indeed needed when working with 2003, at least. If a server has the same SID as a DC, you won't be able to log on to the domain from that server. Since you have to be able to do that (for example, to authorize a DHCP server) you still need NewSID.
For your WSUS issue it's not the SID but the SUSID in the registry you need to delete.