I can see a few alternatives:
* Advertising
"Windows better than everything..." advertising campaign might be one. Massive consumer bombardment with "Windows 7" ads similar to what they did with Windows 95.
* Hardware
Microsoft might follow Apple and Oracle, and start making their own hardware. Massively parallel chips geared towards both the vector and regular computations would be one idea.
Alternatively, their own servers (totally not their market segment, plus they will aggravate their relationship with Dell and others, so this is less likely.
* M & A...
Buying Yahoo? Or better yet - Novel? That would be an interesting development. Novel has very little influence compared to their former glory, yet some of their technology (Moonlight?) might be valuable to MS. So instead of discrediting Mono project, MS might simply jump on it and start offering various open source solutions ... I know I'm daydreaming...