GOOGLE last week unveiled plans to move into the PC operating-system business, taking direct aim at technology’s best franchise: Microsoft Windows.

Google will open-source the Chrome OS software, and give it to PC companies for nothing. That is certainly an alluring price, which is no doubt why Acer (2353.Taiwan), Lenovo(0992.Hong Kong), Asustek Computer (2357.Taiwan), Toshiba (6502.Tokyo) and HP (HPQ) have signed up to work with Google on the project.

If nothing else, the threat of a free Google OS could pressure Microsoft to cut the prices it charges these companies for Windows.

The software won’t be available for a year or so-a year during which Microsoft will be cranking out Windows 7, a well-reviewed and eagerly awaited version that debuts in October.

The battle is served….