Preboot Execution Environment (PXE) refers to various methods of getting an IBM-compatible computer, typically running Windows, to boot up without the need for a hard drive or boot diskette. The methods evolved from the era before computers had internal disk drives.
PXE usually involves booting a computer from firmware -- data contained on a read-only-memory (ROM) or programmable read-only-memory (PROM) chip -- rather than from data contained on magnetic media. This gives rise to the terms 'PXE boot ROM' or 'PXE boot PROM' (sometimes written 'PXE bootprom'). Booting from ROM or PROM eliminates the reliance on an electromechanical device (the physical drive). This enhances reliability and eliminates drive read errors. With today's memory technology, booting from ROM or PROM is fast. PXE can be also used to boot a computer from a network.