Replacing CPU in Dell Dimension 4500 605

Very simply, I think that the tech at the shop is bullpooting you. Both IBM and Dell P4 systems use absolutely standard Socket 478 ZIF sockets. The differences among Dells, IBMs, white boxes and other brands are in the choice of materials for the retention mechanism, heat sink and cooling fan arrangement.

If you choose to involve a computer shop again, pick another one, preferably one that does not induce fear, uncertainty, and doubt about brand-name systems, a behavior common to many small computer shops and maybe even the big ones.

Why do you think that the CPU is bad? What symptoms are you seeing?

Withing reasonable limits, you can use most any Socket 478 CPU in the 4500. See the Dell web site for the exact limitations re. front-side bus speeds, which will rule out some of the faster P4s. Sometimes a BIOS will not recognize a CPU if the manufacturer has not planned for and tested it... Ben Myers