There’s a reason most PC manufacturers are panicking in the face of Apple’s near unstoppable growth – Apple is now hitting the OEM PC manufacturer’s sacred cow, enterprise IT.

Forrester Research looked at 10,000 IT workers around the globe and found that 20% use at least one Apple product for work; 11% are using iPhones, 9% are using iPads and 8% are using Apple Mac PCs or Macbooks.

In addition, Close to 50% of firms now issue Apple Mac PCs in some capacity to their workers, up 4% from the year prior.

While this is by no means a sign of the apocalypse for enterprise manufacturers, it is a sign of increased consumerisation and perhaps the beginning of a fundamental change in enterprise IT. Apple already dominates several markets in the consumer sector, and this is starting to bleed into enterprise, especially at managerial and IT levels.

Managers and execs are more than twice as likely to use Apple products. Younger info workers are also twice as likely to use Apple products as older ones, and there is a correlation between income and usage – 43% of workers earning more than $150,000 use apple, 19% of those earning below $50,000. The decision makers in companies are now setting the agenda.

Apple has made it very clear that it is focused on creating products for individuals, rather than enterprise IT. This strategy appears to be working as these same individuals are becoming the very evangelists that are driving its products into the workplace.

"CTOs [are] bringing their personal gear to work and figuring out what they could do to make it work, often with little or no formal IT support," said Frank Gillett one of the Report’s authors.

While Microsoft remains absolutely dominant in the workspace, Forrester says that Apple is present in some form or another with 41% of executives. Coupled with Microsoft’s absence on mobile devices such as tablets and smartphones, the report is blunt:

"This signals that Windows’ dominance is at an end. In a fragmented market for mobile devices, customers and partners will look to anoint a solid number two alternative for a full range of personal technology – and they’ll choose Apple because of its strength with individuals across smartphones, tablets, and Macs."

The report also states that it expects Apple to become the largest tech company by revenue in 2012, passing HP and Samsung’s $127bn and $134bn respectively. This looks safe, given Apple posted $46.3bn in the last quarter.