Microsoft has kicked off the public beta testing of Windows Vista Service Pack 1.

Vista product manager Nick White confirmed that the limited beta release was given out to testers on Monday via Microsoft's Connect programme.

No date was given for a larger testing phase, but Microsoft hopes to have the final version of Vista SP1 completed and distributed to customers by March 2008.

In addition to a cumulative update of security and stability fixes, Vista SP1 is expected to include improved file indexing and drive encryption software.

Beta tester Brandon LeBlanc outlined his initial impressions on the update in an article posted to the Windows Experience blog.

LeBlanc noted that, while there is little difference to the user interface, the update provides a noticeable improvement in what he termed "overall responsiveness".

Tasks such as calling up the log-in screen, waking from sleep mode or copying files between directories are faster, according to the tester.

LeBlanc also said that support for multiple monitors has been improved and should be more reliable.