Microsoft is a mover and a shaker, and a lot of companies look to Microsoft and companies like it for direction. Whether or not it spurs green investments, it's a step in the right direction for the planet and the environment. If other companies get on board, it's just "gravy."
Other companies will want to compete with Microcoft and do the same thing because it is going to be a big selling point in the very near furture. This may even cause the cost of renewable energy to go down as more sources become available and more people use renewable energy.
If a major company like Microsoft is publicly committing to renewable energy, hopefully other will follow suit. Hopefully there will be more interest in investing in green companies and building green facilities. Hopefully those facilities will make products that will go into creating green data centers and other environmentally friendly businesses.
When a company as large as Microsoft makes such a big change, other people follow suit. Either smaller companies will mimic the change that Microsoft has made for publicity's sake, or companies will start research into new renewable energy technology for the sake of contracts with Microsoft.
If nothing else, the change will potentially lead to cheaper renewable energy options, which would catalyze a larger switch to renewable sources.
Yes, this will spur green investments because people will see the economic value in going green. Once money is involved, people are more likely to work in their own best interests. Whether they want to help the environment or not is another story. But this will lead to more green policies.