1. A method for loading a segment register in a microprocessor operable in multiple modes, said method comprising the steps of: receiving a segment selector for a corresponding segment register load, said segment selector specifying a descriptor stored in a corresponding descriptor table; issuing a plurality of conditional load operations to a memory subsystem, wherein each of said plurality of conditional load operations specifies loading of a descriptor from a corresponding descriptor table; checking, in said memory subsystem, said segment selector associated with each of said plurality of conditional load operations to determine whether said segment selector specifies a descriptor table corresponding to said descriptor; executing, in said memory subsystem, one of said plurality of conditional load operations if said segment selector specifies a descriptor table corresponding to said descriptor; writing said descriptor corresponding to said segment selector to a temporary segment register if said segment selector specifies said descriptor table corresponding to said descriptor; writing invalid data to said temporary segment register and identifying said invalid data as invalid if said segment selector does not specify a descriptor table corresponding to said descriptor: and loading said segment register, by utilizing said descriptor and selector, in accordance with an operating mode of said microprocessor.