The global supply of hard drives is estimated by Digitimes to be 4-6 weeks and will likely be exhausted by December. The shortage could result in a 10% shortage of PCs in the four months from 2011-12 to 2012-3. That would mean a 3% (1/3 year X 10%) drop in PC production for 2012, not good for M$, PC makers, retailers and consumers. Likely prices will rise to ration the scarce resource.
On the other hand, it may give further impetus to extend the life of PCs and to go to small cheap computers like low-end x86 or ARM. Perhaps GNU/Linux and Android/Linux will stronger growth as a result. If you have to pay more for the hard drive, you may want to pay less for the OS or buy a really small cheap computer instead of a big box.