You cannont enable VMQ on the Intel® PRO/1000 PT Quad Port Low Profile Server Adapter. The Intel® PRO/1000 PT Quad Port Low Profile Server Adapter is an older adapter that launched in 2007. Only the newer adapters have support for VMQ. Use ark.intel.com to compare adapter specifications and look for VMDq support.
http://ark.intel.com/compare/50495,59063,49187,49186 compares the available quad port copper adapters. The product briefs for each adapter have more details than you can find on the ark site, but this is a good place to start for making quick comparisions.
I hope this helps.