I've just been tearing my hair out about similar problems to you, lock ups etc. And replacing the RAM fixed it. Not being a memory expert I cheat a bit if you go to the Dabs site Dabs.com and click on Crucial in manufacturers they have a memory configurator which will tell you exactly what you need, I put your board in it and what you need is SDRAM CL2 Non Parity either PC100 or 133 depending on your bus speed, in your case PC133. Just look on the web for this or buy it from Dabs. Since your have 2 slabs of memory in, take out the new memory and run the computer for a couple of days that will certainly tell you if its the memory. Oh and cheap memory is poorer quality as I'm sure some of the others will tell you.