Microsoft will release five sets of security patches next Tuesday, but only one is "critical," and it targets only Windows 2000 machines.

With the remaining four security updates rated “important,” this latest round of patches appears to be less worrisome than the August updates. Last month, Microsoft released nine updates, six of which were rated critical.

Microsoft rates its bug-fixes as critical when attackers can exploit the flaws without requiring any user action.

Also set to be patched this month are Visual Studio, Windows Services for Unix, SharePoint Services, and the Windows Live and MSN Messenger software.

Microsoft releases its security patches on the second Tuesday of each month, generally around 7pm, UK time.

With this latest round of patches, Microsoft will have released 55 updates in 2007; the same number it had released by September of last year.