Since the introduction of Microsoft latest operating system Windows Vista,most of the PC buyer are forced to purchase the systems that run the Windows Vista.The three giant PC vendors Dell,HP and Lenovo are also pushing towards Vista aggressively as Microsoft will stop allowing any vendors to preinstall Windows XP on new systemNevertheless, still there are a number of high performances, inexpensive business PCs that come with both Windows Vista and Windows XP options. These are Dell OptiPlex740, the HP Compaq dc 5750 and the Lenovo 3000J115. Despite their $1000-1250 cost range, all three models came with large wide-screen LCD monitors. They are preferably design to support small business setup as all three systems are based on business’s PC-based cash-register system with higher level of security, reliability, service and support.Although all three systems are comparable to their performance and business class features, yet Dell OptiPlex 740, with 2.2 GHz Athlon 64X2 processor, 160GB Hard drive capacity, superior mini-tower case design with horizontal orientation and super quiet operation has advantage over the HP Compaq dc 5750 and the Lenovo 3000J115. The ultra compact PotiPlex 740 can be mounted at the back of 17 inch LCD monitor. The OptiPlex’s hard drive has been installed perpendicular to casing in plastic sleds with rubber mounts to avoid the vibration. Slot cuts are made into the interior of OptiPlex 740’s case to mount the optical drives without screws.