With DIMM modules becoming the industry standard in a market dominated by SIMM modules, purchasing memory has gotten much more complicated. Newer motherboards require specific speeds of DIMM's and compatibility is an issue. Memory should be purchased with the motherboard to ensure compatibility. Always refer to your motherboard manual to check jumper settings for the correct processor speed, voltage, cable directions, etc. Ground yourself before handing your new motherboard.
Static electricity causes damage which produce intermittent errors that are hard to diagnose.
Make sure motherboard cables are installed in the correct direction. Use the correct fans for your Processor. Some Processor may require bigger heatsinks such as the AMD K6 Processors, otherwise you may get error messages running Windows 95. If system does not boot, methodically remove one component at a time starting with the hard disk and floppy disk flat cables. Turn on the system after each component is removed and perform a process of elimination.