Although the Tablet PC has few supporters and it hasn't succeeded to impress many users, Bill Gates continues to back this format. Microsoft's chairman restated his trust in the Tablet PC and emphasized the necessity to invest furthermore in hardware and software.

It's been 4 years since Gates said that the Tablet PC is a format that has no limits. In 2001, he estimated that in the five years this type of PC will become the bestselling PC from US.

Unfortunately, the evolution of the Tablet PC has been more than slow, the form factor managing to score significant sales only on the health care and insurance market.

According to IDC, in 2004, 640,000 Tablet PC units were sold, and this year, they estimate 1.2 million, which means 2 percent of the portable PC market.

"We need to keep investing, both in the hardware and software side, before it moves into the mainstream," said Gates at a news conference here on Monday. "It's not yet in the mainstream. I totally believe in the tablet."

The analysts agree that Longhorn will boost Tablet PC sales, estimating that by 2007 the sales will reach 4.9 million units, and in 2008, vendors will reach 9,7 million units, which is approximately 11% of the market.