According to me HP and Compact give away gifts more then others do.
They include gift worth rupees 1000/- or more.
Dell is the costliest among all.So most the people purchase HP,Compact or Lenovo.
I had bought a Lenovo Desktop before in 2005 they had gifted me a Pen-drive,a CD pack and mouse pad with a discount on overall system.
But now in 2010 gifts are more advanced,they include printer,Britannica,table,UPS and many more BONANZAS.
I case of other brands I don't have much idea.
Best of luck