PC Diagnostic Software

The company I work for does periodic maintenance on a lot of Intel-based PCs. We have a diagnostic program which fits on a floppy and does a basic test of the RAM, CPU, and motherboard resources. Unfortunately it’s out of date and won’t work on newer machines. Does anyone know of a good program for this kind of thing? It needs to be fast, portable, and its tests have to give understandable results. Oh, and ideally it should cost less than $500.