A legacy network adapter works without installing a virtual machine driver because the driver is already available on most operating systems. The legacy network adapter emulates a physical network adapter, multiport DEC 21140 10/100TX 100 MB. A legacy network adapter also supports network-based installations because it includes the ability to boot to the Pre-Boot Execution Environment (PXE). The legacy network adapter is not supported in the 64-bit edition of Windows Server 2003 or the Windows XP Professional x64 Edition."
then you can see as below