promble upgrading my HP kayak

[dena]

I HAD A PROBLEM WITH MY HP KAYAK XA 6/266 PRODUCT NUMBER D4799N.
I WANT TO UPGRADE MY RAM USING SDRAM PC133 128 MHz AND WINDOWS 98SE
AFTER I PLUG MY RAM, MY SYSTEM BECAME UNSTABLE AND I COULDN'T FINISHED MY WINDOWS INSTALLATION.
CAN SOMEONE GIVE ME OPINION TO SOLVE THESE PROBLEMS?