REDMOND, WA — Almost one month after it pulled an earlier release of Vista Service Pack 1 because of driver-compatibility issues, Microsoft has released what it says is a version that should be nearly bug-free.That is, unless users’ systems employ one of a handful of drivers the company hasn’t yet incorporated into the new code.

Microsoft made Vista SP1 available for download on Tuesday. The product will begin downloading automatically in mid-April (on systems set to allow that sort of behavior). It remains unclear when SP1 will be available on retail shelves, although Amazon.com said it would begin shipping boxed copies of the update on Wednesday.

But back to those problematic drivers…

A list of the problem children is available in Microsoft’s Knowledge Base (http://support.microsoft.com/?kbid=948343#method5). The company claims very few remain to be fixed, but if the system to be updated contains one of them, the update will halt automatically before system stability is compromised. That was an issue with SP1’s earlier version: Some users complained bitterly about losing entire hard drives full of documents to incompatibility issues that forced them to reformat their hard drives and reinstall the operating system from scratch.

Microsoft Product Manager Nick White wrote on the company’s blog, “…Windows Update will recognize PCs with drivers that may be problematic and postpone offering SP1 to those PCs until it has installed corrected drivers or other applicable updates. Either way, Windows Update works to detect whether or not your system is ready for SP1 and not offer it to you until the time is right.”

SP1 is available in five languages: English, French, Spanish, German and Japanese. Presumably all of them carry the same caveat.