First-tier notebook brand vendor Hewlett-Packard (HP) is set to start selling its WebOS 3.0-based tablet PC, TouchPad in April with shipments to start delivery by the end of March, according to sources from HP’s upstream component partners.

The sources pointed out that HP internally is aiming to ship 45-48 million notebooks and tablet PCs combined in 2011. After deducting the volume of HP’s notebook shipment forecast, HP’s TouchPad series product shipments in 2011 are forecasted to be around 4-5 million units.

Since HP has adopted panel that support 1024 by 768 with aspect ratio of 4:3 for its tablet PC, different from most of Android’s 16:10 design, the sources believe if HP fails to challenge Apple’s iPad, the company will have great difficulties to regain its pace in the tablet PC market in the future.

In addition to tablet PCs, HP is also expected to start coordinating its smartphone products with WebOS platform to allow the platform to function with the company’s different products