Crashing with AMD K6 2’s

Our organisation has just purchesed 27 new pc’s. They are AMD K62 500’s with 64Mb of Ram, onboard graphics and sound cards. We have set them up to work on a network using 10/100 Fast Earthnet PCI adapters. The AMD patch has been installed sucesfully. We are using W95 as an operating system. The problem is that when the machines have been running for about and hour maybe less some of them crash, shutoff, blue screen, or just dispay the flashing DOS cursor. We have tried reinstalling windows 95,putting the components back in etc. We are running out of ideas so any help would be appriciated.