Acer has filed patent counterclaims against Hewlett-Packard as both companies continue to tussle for a larger share of the global PC market.

Acer, the world's third-largest PC vendor, filed counterclaims in the US District Court for the Western District of Wisconsin and with the US International Trade Commission, alleging that HP, the world's largest PC vendor, infringed on patents related to personal computers servers and peripheral devices.

Acer would take all necessary steps to protect and enforce its patented technologies, with or without a legal proceeding, it said in a statement. An HP spokesperson said the company had no comment.

HP first sued Acer for patent infringement in March, seeking compensation from Acer and its US subsidiary for allegedly selling PC products that infringe on patents related to optical drives, clock frequency switching and power consumption. HP filed another patent infringement suit against Acer and its US subsidiary in April for allegedly infringing on PC patents related to power savings, heat management, regulating the flow of data and improving screen picture quality.

Acer vowed to strike back when chairman, J.T. Wang, announced in April that the company had retained intellectual-property lawyer, Chris Ottenweller, of Orrick, Herrington & Sutcliffe for its defense against the lawsuits. Acer in July filed a counterclaim against the HP's two lawsuits, alleging HP infringed its antenna and DVD-ROM head technology patents.

The lawsuits come as Acer increases its US and global presence at a brisk rate. The company extended its lead over Lenovo as the world's third largest PC vendor with the recent acquisitions of Gateway, a US PC vendor, and Packard Bell, a European PC vendor. During the third quarter this year, Acer recorded a 59.2 per cent increase from the previous year in global PC shipments, drawing closer to HP, which recorded a 19.6 per cent increase, according to an IDC survey.