The first thing I would look at is check to see if your CD is clean and not scratched. Run a cd cleaning disk in the drive. Some cd roms are very sensitive to surface defects on the disk, so you might even try swapping cd drives in your pc's. If the cd appears dirty, use a cd disk cleaner or try pouring a little alcohol on the disk and gently rub the surface with a small bit of CLEAN soft cotton cloth, such as a well worn undershirt etc. DO NOT use kleenex or similar products as this can scratch the disk surface wven worse. Rub the disk in a motion from center to outside edge, not in a circular motion around the disk. rince under cool water of a faucet and pat dry.
IF the cd is scratched badly, sometimes you can polish out those areas with toothpaste, but be careful to not over do it. Then rinse and dry as stated above.

If you have bad ram it should show up in the ram test at boot up,and most modern systems will lock up at this point if bad ram is detected. Also you can always remove your ram strips one at a time and see if the problem goes away, as its unlkely all your ram strips went bad at the same time.

Lastly your message said you had pc100 ram and were going to pc133. the pc133 should run at the slower clock speed ok but do not mix pc133 with pc100. That will cause problems also.