A stark assessment from The Economist:
The personal computer spawned a new industry. But many of the firms that initially flourished in the PC era are now finding life difficult. Dell, the leading PC-maker, issued a profit warning last week that sent its share-price to a five-year low. Intel is trying to regain ground lost to AMD, its increasingly confident competitor. Microsoft has just announced that it will buy back 8% of its shares for around $20 billion—a sign that its high-growth days are behind it.
The article goes on to explain that the market leaders are in relatively good shape -- compared with the vendors in the following graph: