get memtest86..
http://www.memtest86.comThat\'ll test your memory without windows, its a true test for memory.
If it passes ALL passes fine, it\'s not your memory. If you get errors then i\'d say your new mem is screwed. You can try moving your memory around and testing it in different dimms (the memory slots)
Make sure your PSU does support it\'s rated wattage. I\'ve seen a lot of psu units not support what they say they support. Each rail only can carry so much wattage.
This may help in choosing a new psu unit.
http://www.procooling.com/articles/html/picking_psu_s_for_athlon_syste.phpAs for what wattage rating you really want. Out of my own experience. 400watt is the minimum to run a p4 or Xp system imo. You\'re pretty much guaranteed stability with a psu 400watt or higher.
If you want to know what your system is drawing of the psu. Volts x Amps = Watts..