While there has been much speculation as to when Vista Service Pack 1 will be released to production, John Curran, head of Windows Client Group at Microsoft told us: We are very close to the finishing line. It will definitely be in the first half and I would be so bold as to say it will be in the first quarter.

Curran said that Service Pack 1 brings incremental improvements to Vista’s security, performance, and reliability. He said it also sees improvement in Vista’s integration with Windows 2008 Server, formerly codenamed Longhorn.

But while he stressed that the first release of Vista even before SP1 is added is stable, secure, and reliable, he acknowledged that some corporate customers in particular have been waiting for the launch of SP1 before they upgrade from Windows XP. The launch of the first service pack does tend to be a key motivator (for enterprises to upgrade), he said. It is definitely one of the events that seems to trigger a move from evaluating the latest version to actually deploying it.

Curran said that as a result of the launch of Vista SP1, Microsoft expects to see more activity in our [financial] second half, which for Microsoft runs from January to June. But he stressed that Vista adoption even prior to the launch of SP1 is in line with the firm’s expectations.

The migration to Vista has been faster than we saw with the migration to XP, he said, and we have now sold over 100 million copies of Vista worldwide.

Microsoft launched Windows Vista on January 30 last year.