4. Xobni

Xobni's Outlook plug-in delivers excellent search and statistics, and it also grabs additional information from services such as LinkedIn and Facebook. The platform could link Outlook with all kinds of things such as customer relationship management software or other business applications, and owning Xobni would enable Microsoft to ensure that it developed for Outlook and Outlook alone. Techcrunch says that Xobni has already rejected a "sub $20 million" offer from Microsoft, but in the current economic climate another (lower) offer might be more warmly received.

5. Palm

Buying Palm would bring the Pre's designers to Windows Phone, and it would annoy Steve Jobs, too: the current team includes Jon Rubenstein, former vice-president of Apple's iPod division, and former Apple developers' champion Chuq Von Rospach.

Andrew Kitson, senior analyst with Juniper Research, suggests that a Microsoft smartphone would be a nice thing to sell in Microsoft's forthcoming retail stores. Should it be a Palm? "The question comes down to cost," he says. "Would it be more cost-effective to buy an existing player such as Palm, or to just develop a handset family and brand internally?"

As Kitson points out, the Pre is a business device where Microsoft needs a cool consumer phone, and making Palm's WebOS work seamlessly with Microsoft products might not be easy. "It might be better to come up with a new iteration of Windows Mobile - but if they dump the OS, what's the point of buying the business?" Microsoft needs "to come up with a really exciting, definitive and iconic device to capture imaginations, much like the iPhone did when it first appeared. Now everybody's emulating the iPhone. Does that sound like the Palm Pre?"

If the Pre doesn't sell truckloads, Palm's days may be numbered. "Somebody's going to buy it before it goes under, or they might wait until Palm expires, stroll in and buy the assets they really want at a knock down price," Kitson says. "But it could take a couple of years [for that]. Can Microsoft wait that long? Not with Acer, Dell et al piling into the market."

6. Facebook

While Facebook isn't making enormous sums of cash Microsoft has deep enough pockets to finance it indefinitely and use it to boost other Microsoft services such as Windows Live Messenger, Live Mesh and so on. All that user data is a potential money pot, too: it's not searchable by traditional search engines, so whoever has access to Facebook's profiles, details and connections can offer advertisers and searchers something that Google can't.

Microsoft already has a small share in the site, but Facebook boss Mark Zuckerberg shows no sign of wanting to sell his baby. If he changed his mind Microsoft wouldn't need $15 billion, though: according to leaked internal documents, even Facebook doesn't think it's worth that much. The real figure, Associated Press reports, is $3.7 billion. Microsoft could find that much down the back of the sofa.

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