Google is getting involved in an handbags at dawn fight with Microsoft. For the last year Microsoft has spent much of the past year taking shots at competitors through advertisements. Now Google is starting some Microsoft-focused advertising of its own.

A billboard advertising campaign targeting users of Microsoft Office has started. Over the next four weeks, billboards in Boston, Chicago, New York and San Francisco will illustrate how an anonymous IT managers' struggles with Office leads him to recommend that his company switch to Google Apps.

Microsoft will offer Office Web Applications next year. This is a lightweight version that run in a Web browser and will be available in advertising-supported or subscription versions. Microsoft hasn't revealed pricing for the subscription versions yet. Google Apps Premier edition is $50 per user per year, but the Standard edition costs just $10 per year for a domain name.

Google's billboards focus on the high cost of software upgrades as one of the advantages of using Google Apps. This is the same strategy that Microsoft used to great effect on Apple through its Laptop Hunters campaign.