These adapters will allow you to install LGA771 Xeon processors on an LGA775 motherboard.
This is an inexpensive way to add a Quad Core Processor to the 775 board. Also 775 boards will have overclocking abilities allowing you the speeds of the more expensive Core2Quad processors.
A very important thing before proceed with this mod, is to ensure that TDP & FSB of your motherboard must equal or higher than your CPU.
Some LGA775 motherboard chipsets are incompatible or have limitations with the detection of Xeon processors.
Also some (not all) ready build systems like (Dell, HP, Fujitsu, Shuttle e.t.c) have known compatibility issues with this mod, due to their motherboard's chipset limitations.
Chipsets Q45, Q43, Q35, Q33, X38, X48 are not compatible (at least with 5.xxx series Xeon).
Chipsets P45, P43, P35, P31, P965, G45, G43, G41, G35, G33, G31, nForce 790i, 780i, 740i, 630i, GeForce 9400, 9300 should work ok.