frequent system freeze

my 4 yrs old AMD athlonXP1600 suffered frequent system freeze recently. i reinstall XPpro clean but problem won’t go away. this also toasted 1 of 256mb ram in dimm slot#2. wondered what’s the cause & any solution? my pc spec are: msi kt266pro2ru, 512mbddr, 2 hdd, 1 dvd player & 1 burner w/ 300w codegen PSU.