Microsoft has started soliciting volunteers to beta test an ad-supported version of Office 2010 that will provide feature-limited versions of the company's two most popular applications. Did we mention it's free?

Technology enthusiast site Think Different published what details are known about the beta on Thursday.

"While we still wait for the public beta of Office 2010 to release, hopefully at PDC09, Microsoft has sent out invites to Office Live Workspace users to try out the new Office Starter 2010 Beta SKU," a posting on the site said.

In early October, Microsoft (NASDAQ: MSFT) explained the concept behindOffice 2010 Starter on its Microsoft Office 2010 Engineering blog.The package, which will be ad-supported and therefore free when it's released, will provide bare bones versions of Word and Excel -- the two most used applications in the overall Office suite.

"Office Starter 2010 is a reduced-functionality, advertising-supported version of Office 2010, available exclusively on new PCs. Office Starter 2010 will provide new PC owners with immediate exposure to the Office 2010 experience on new PCs right out of the box," the blog post said.

Officials, however, have not said what features will be in or out of the Starter versions.

According to the post, Office 2010 will replace Microsoft Works on new PCs and will include a way for users to upgrade to a "fully-featured" version of the product from within Starter.Don't get antsy to try it right away, however.

As explained in a copy of the invitation to apply for the beta test, published by Think Different, prospective participants will need to fill out a short questionnaire. In it, they're asked questions such as what products they use to compose documents and which version of Windows they're currently running.

"All you need to do is use Office Starter 2010 Beta at home over the next few months, and let us know what you think," the purported invitation says.

Microsoft started a technical preview of Office 2010 in July at its annual partner conference.

Web-based versions of Word, Excel and PowerPoint

In mid-September, the company began a preview of Web-based versions of Word, Excel, and PowerPoint. Those versions will also be free to most users.

Microsoft officials, meanwhile, had no comment regarding Office 2010 Starter other than a typically boilerplate response.

"As previously announced, Office 2010 will reach the beta milestone in November. Other than this, we do not have anything else to share at this time," a Microsoft spokesperson said in a statement e-mailed toInternetNews.com.

Microsoft's release of betas of all three versions of Office 2010 are expected by many to come at next week's Microsoft Professional Developers Conference 2009 (PDC09) in Los Angeles.