Symantec has released a free tool that wipes spurious entries from Windows' registry that had crippled some PCs running the company's security software after they were upgraded to Windows XP Service Pack 3 (SP3) or Vista SP1.

The tool, SymRegFix, had been promised by Symantec two weeks ago when users reported that upgrading to XP SP3 emptied Windows' Device Manager, deleted network connections and packed the registry with thousands of bogus entries.

Symantec initially blamed Microsoft for the snafu, but later accepted some responsibility. Last week, the company said the combination of a Microsoft process and the SymProtect feature of its Norton-branded consumer security software had added the errant registry entries, and it told users to turn off that feature before upgrading.

SymProtect, designed to protect Symantec's security software from being hacked by malware, guards against unauthorized changes to the registry.

Reese Anschultz, a senior Symantec manager, announced the availability of SymRegFix on a company support forum Thursday.

When some users on that same thread noted that the tool had not deleted all the spurious registry keys, another Symantec employee stepped in. "The other garbage entries may have been created by Microsoft's Fixccs.exe outside of the Symantec registry keys," said Steve Dang.

Earlier, Symantec had identified the Fixccs.exe executable as the Microsoft side of the problem; it had also contended that other security software that monitors registry changes can cause registry pollution, although few incidents have been logged to Microsoft's support forums.

"If you have any other security applications, especially any that monitors/protects the registry, please disable those," said Dang. "Then, open a command prompt and type 'symregfix /override.' This will attempt to delete the garbage registry keys under the entire HKLMSystemCurrentControlSet hive, not just those under the Symantec registry keys."

Symantec has also issued a patch via its LiveUpdate service that prevents the registry corruption from occurring, although users must run LiveUpdate from within their security software, then reboot the PC before attempting an upgrade to Windows XP SP3 or Vista SP1.

That the problem could also affect users updating to Vista SP1 was new information last week; before then, only Windows XP SP3 upgrades had been fingered as causing trouble. In a message posted to the Symantec support forum last Friday, Anschultz downplayed the threat posed to Vista users. "Given how long Vista SP1 has been available relative to the XP SP3 upgrade and the rarity of this issue on Vista, it appears that the FixCCS.exe program doesn't need to 'fix' stuff as often on Vista, but it may on occasion," he said.

Symantec's SymRegFix clean-up tool can be downloaded from the company's site.