In that case take it back to the shop and get your money back. I know it costs more but Crucial guarantee the memory they supply will work and will give you a full refund if it doesn't. Why not get your memory from there?

Now to the next problem. If Windows 98 experiences a power failure, unlike XP or Vista it does not have a built in recovery process. If you are lucky it will restart after a simple CHKDSK scan but if not it could corrupt the registry to such a degree that it will fail to start at all. If you can't maintain a regular power supply to your PC all the time then expect it not to work one of these days.