A new beta of Microsoft's forthcoming Windows Vista Service Pack 1 appeared on the BitTorrent file sharing services over the weekend.

The software was reportedly released as a closed beta. The package is identified as version 6.0.6001.16633 (longhorn.070803-1655). The 684MB file is distributed as an executable .exe file that updates installed systems.

A service pack is a collection of security updates and other bug fixes. The release of Service Pack 1 is generally considered to mark a new level of maturity for the Microsoft software, rendering it stable enough for deployment on corporate clients.

Previous betas for the service pack were distributed as an .iso disk image that contained a fully updated version of Windows Vista that could be installed on a new system or as a virtual guest operating system.

The MS Windows Vista Compatible Software blog posted screen images of the service pack, showing it as an unpacked size of 1.7GB.

The installation of the update required three reboots. After the update Windows Vista is marked as Service Pack 1 v.249.

A spokesperson for Microsoft declined to provide additional information on the service pack, or a projected availability date. The update is generally expected to become available late this year or early next year.